US2338597A - Submarine rescue and escape mechanism - Google Patents

Description

Jan. 4, 1944. c; n. PLEAK SUBMARINE RESCUE AND ESCAPE MECHANISM y 5 Sheets-Sheet 1 File'd Feb. 12, 1940 ATTORNEY J Jan. l4, .1944. c. D. PLEAK VSUBIMRINE REscE AND' ESCAPE MEGHANISM 5 snets-sheet 2 Filed Fe. 12, 1940' ou. R Y mkv. E m e. M, V/e. m mf A M f ww Y B 7 u...

Jan.. 4, 1944. Q D, PLEAK 2,338,597

SUBMARINE RESCUE AND ESCAPE MECHANISM Filed Feb. l2, 1940 5 Sheets-Sheet 3 ATTORNEY.

Jan. 4,/ 1944,. c. D. PLEAK z338,597

SUBMARINE RESCUE AND ESCAPEMECHANISM Filed Febjlz, 1940 5 sheets-'sheet s NVENTOR. Carra/ fea,

ATToRNEYs.

Patented Jan. 4, 1944 UNITED STATES PATENT OFFICE S'UBMARINERESCUE AND ESCAPE MECHAN ISM 3 Claims.

The present invention relates to submarine rescue and escape mechanism, and the primary object of the invention is to provide mechanism, carried upon a submarine vessel, and operable entirely from within the vessel, whereby the crew may escape to the surface from a disabled submarine, and whereby a buoy may be projected to the surface, carrying with it signalling mechanism and means whereby air may be pumped from the surface to the submarine, whereby telephone communication can be established with the surface, and whereby electrical power may be conducted from the surface to the submarine for use aboard the disabled vessel. Further objects of the invention will appear as the description proceeds.

To the accomplishment of the above and related objects, my invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that change may be made in the specific construction illustrated and described, so long as the scope of the appended claims is not violated.

Fig. 1 is a transverse section, more or less diagrammatic, through a submarine, showing the arrangement of my rescue buoy and my escape car and the operating mechanism therefor;

Fig 2 is a horizontal section taken substantially on the line 2 2 of Fig. 1 and locking in the direction of the arrow, the buoy and car having been removed `for clarity of illustration;

Fig. 3 is an enlarged transverse section showing the manner of connection of the rescue conduit with its reel;

Fig. 4 is a top plan view of my rescue buoy in inated condition;

Fig. 5 is a side elevation thereof;

Fig. 6 is an enlarged vertical section through the gas reservoir forming a part of my buoy;

Fig. 7 is an enlarged sectional View of a valve used in connection with the gas reservoir;

Fig. 8 is an enlarged sectional view of connector means for the conduit;

Fig. 9 is an end view of the connector head at the end of the conduit;

Fig. 10 is an enlarged elevation of the buoyejecting means of my invention;

Fig. 1l is an enlarged fragmental sectional view of the water-tight seal formed between the escape car and the upper portion of its compartment;

Fig. 12 is a more or Vless diagrammatic view of the reel for the rescue lconduit and its driving'means; and

Fig. 13 is a similar View of the reel for the escape car cable and its driving means.

The numerous tragedies which have resulted from disablement of submarine vessels while submerged, have been due primarily to the fact that no eiicient means has been provided heretofore for permitting the escape of the crew of the disabled vessel. The rescue bell which has recently come into use is marvelously effective once it is properly attached to the disabled vessel, but, unless all of the circumstances surrounding the vessel are perfect, the bell cannot be attached to the submarine without the services of divers; and often submarine vessels are disabled at a depth such as to make diving impossible. The escape lung is also effective in many cases; but it cannot be used beyond relatively shallow depths, its use subjects the crew members to submersion in water which may be impossibly cold, and it also subjects the users to water pressure which may be highly injurious, and which certainly will be injurious unles the users rise through the water relatively slowly.

When a submarine is disabled while submerged, it sometimes happens that the circumstances are such that if suicient electric power could be supplied to the vessel from an outside source, the vessel could be raised. At other times, the circumstances are such that, if sufcient air could be supplied to the disabled vessel, it would be possible for the crew to make necessary repairs and bring the vessel to the surface. v

1n attempting to overcome all cf these defects of prior art mechanisms and to provide means whereby air and electric power can be supplied. to the disabled vessel from an assisting vessel on the surface, I have conceived the mechanism of the present application.

In the drawings, the hull of a submarine vessel is indicated generally by the reference numeral 29. A11 such vessels are provided with a plurality of transverse bulkheads at spaced locations throughout the length of the vessel; and such a bulkhead is indicated at 2i. In the interest of both space economy and safety, I propose to build my escape and rescue mechanism into one or more of these bulkheads; and in Fig. 2,1 have shown how this can be done. The longitudinal depth of the bulkhead is increased as at 22 by providing walls 23 and 2t to form a room l5 communicating with the body of the vessel through doors 26 and 21. All of the controls for the mechanism of the present invention are yaccessible from within the room 25; so that, even if a part of the vessel is ooded, the doors 26 and 21, or that one of those doors which is adjacent the ilooded portion of the vessel, may be closed to prevent flooding of the room 25, and so that the rescue and escape mechanism of the present invention may be operated from the protected room.

A door 28, which is water-tight when closed, provides access from the room 25 to a water-tight chamber 29 having a long, vertical, cylindrical portion 36 which opens at 3| through an outer wall of the vessel. The port 3| is normally closed by a hatch 32 of standard and well known construction which may be locked, unlocked, and removed by any known mechanism for so manipulating hatches. Within the chamber 29 is mounted a reel 33 upon which is wound a flexible, but armored, conduit 34. The reel 33 is preferably connected to be driven by an electric motor 35, through a gear reduction 36; and one end of the conduit 34 is suitably connected to my rescue buoy indicated generally by the reference numeral 31 in Fig. 1, said buoy being normally carried in the cylindrical portion 36 of the chamber 29.

The reel 33 comprises a hollow shaft 38 which carries an elbow 39, shown in Fig. 12 and in detail in Fig. 3. The conduit 34 is formed at its opposite ends with connector heads 46 and 44. The head 40 cooperates with a connector head 4| on a long tubular element 42 forming a part of the buoy, and may be secured thereto by any suitable coupling means such as the swiveled coupler 43. The head 44 is similarly connected to the elbow 39 through any suitable means such as the swiveled coupler 45. The conduit 34 is formed to provide an air passage 45, an electric power line 41, a telephone line 48, and any other desired conductors, extending from end to end thereof. The elbow 39 and the head 44 are formed with cooperating connector elements similar to the elements |52, |53, |54, and |55 of Fig. 8, whereby, when thehead 44 is brought into cooperative relationship with the elbow 39, operative connections will be established between the gas passage 46 of the conduit and the gascarrying tube 46 in the elbow, between the power line 41 of the conduit and the power line 49 of the elbow, and between the telephone line 43 of the conduit and the telephone line 59 of the elbow. As is clearly shown in Fig. 12, the conductors 45', 49, and 5|) extend axially through the shaft 38, and are operatively connected through a standard swivel coupler to stationary conductor lines (not shown) The power and telephone lines will be continued to a central switch board, the controls of which will be accessible in the room 25, and the air conduit will be continued, through valved pipes, to distribute air to desired portions of the vessel.

Corresponding conductors |48, |49, and |50 extend throughout the length of the tube 42, terminating in a coupler head 5|, similar to the head 4|, at the uppermost end of the tube 42.

The tube 42 forms a supporting base for the buoy 31 and for the gas reservoir indicated generally by the reference numeral 52 and illustrated in detail in Fig. 6. Said reservoir comprises a cylindrical shell 53 within which are fixed upper head 54 and lower head 55, said heads being secured likewise to a central sleeve 56 which is sleeved in place on the tube 42. A base 51, having a plurality of ports 58 therethrough, supports the reservoir in position on the tube 42; and said base is formed with a radially extending annular flange 59 for a purpose later to be described. At the upper end of the shell 53, there is provided an annular shoulder '60, the purpose of which also will be described hereinafter.

It will be seen that the base 51 cooperates with the head 55 to provide a chamber 6| open to the circumambient medium; and the reason for this will appear hereinafter. A nut 62 secures the reservoir assembly in place on the tube 42.

A bracket 63 is sleeved in place on the tube 42 immediately above the reservoir 52, said bracket and reservoir being provided with cooperating elements 64 to prevent relative rotation thereof. The bracket 63 is provided with an upstanding flange 63 to which is secured the lower end of an air-tight bag 66 which should be formed of any available air-tight material capable of being readily folded and collapsed. I prefer to form the bag 66 of material which is nonelastic; but the essential characteristics of the material are that it shall be air-tight, unaffected by sea water, readily foldable, tough, and of high tensile strength. The lower end of the bag is secured to the ilange 63' by means of a band 61 held in place on said ange by a plurality of bolts 68, or the like; and of course the joint must be air tight.

It will be noted that the upper end of the shell 52 terminates short of the bracket 63, leaving a space 69 therebetween, and dening a chamber 10 open to the circumambient medium.

Referring, now, to Figs. 4 and 5, it will be seen that the bag 65, when in inflated condition, is surrounded by a protecting shield consisting of a plurality of toggle elements. When deated and collapsed, the bag 66 is much more closely sur,- rounded by the said toggle elements, as is apparent from an inspection of Fig. 1.

Adjacent the upper end of the tube 42 there is secured in place a bracket 1|, the same being held in place by a nut 12 or the like. A plurality of bars or shield elements 13 are pivotally secured to a like number of radially projecting arms 14 upon the bracket 1|, said shield elements 13 being mounted upon pivots 15, the axes of which lie in planes substantially perpendicular to the axis of the tube 42, and are arranged in an annular series.

Slidably mounted upon the shell 52 is a second bracket 16 formed to provide a plurality of radially extending arms 11 carrying pivots 18, said pivots being arranged upon axes lying in planes substantially parallel with the planes of the pivots 15. A coiled spring 19 surrounds the shell 52, is supported on the flange 59, and constantly urges the bracket 16 upwardly toward engagement with the flange 6B. A plurality of shield elements 89, similar to the elements 13, are pivotally mounted on the pivots 18; and the free ends of the elements are hingedly connected to the free ends of the corresponding elements 13 by hinge means 8|, or the like.

Obviously, if the bracket 16 is pressed downwardly against the tendency of the spring 19, the shell elements 13 and 89 will be straightened and brought into the positions of Fig. 1, while the bag 66 will be collapsed. However, when the bracket 16 and the shield elements are released, the spring 19 will force the bracket 16 upwardly to the position of Fig. 5, thereby expanding the shield elements.

Suitable latch means (not shown) may be provided for holding the bracket 16 in its lowermost position; and if such means is used, the latch must be released before the buoy is ejected from the vessel, such release being effected either manually or by automatic means such asa pawl ladjacent the mouth'l of the chamber 30.

However, such latch means is not essential; since the shield elements will be held .in their straightened position, whenever the buoy .is in the chamber 30, by engagement with the Walls of that chamber; in which case, the force of the spring 19 will tend to assist in the ejection of the buoy after the hinges 8l have passed the mouth 3| of the chamber 3e.

Returning to Fig. 6, it will be seen that there is positioned in. the chamber 6'! a pressure-responsive instrument 32 which may 4be either a diaphragm or a bellows or a piston. Such element 82, however, supports a `column of liquid in a pipe 84 extending upwardly through the head 55, into the reservoir, and communicating with the lower portion 85 of a pressure-responsive valve indicated generally by the reference numeral 86. A hand-operated valve 8,3, normally in closed position, prevents movements of the pressure-responsive element 82 from being communicated to the valve t6 under normal conditions.

Valve 86 is provided with a port 8l constantly in open communication with the interior of the reservoir 52 in which is contained air or other gas under very high pressure. A pipe 88 leads from the outlet port of the valve 35 through the head til, through the chamber le, and through the bracket 53, to the interior of the bag BS. Another pipe te leads from the interior of the bag 65 to the upper end 9e of the valve 8e. Within the valve housing is reciprocably mounted a piston-type valve el formed with heads 92 and Q3 respectively received in the lower and upper parts of the valve housing, and formed with a passage @il which, in one position of the valve, will establish communication between the port 8l and the pipe 88.

It will be seen that the head e2 is larger than kthe head 93, and that the pressure of the circumambient medium is impressed upon the head 92 Whenever the valve 83 is open, while the pressure within the bag 65 is impressed at all times upon the head 93.

@ne form of valve which may be used at 83 is illustrated in Fig. 7. As illustrated, such valve may comprise a casing 95 having a passage 9S therethrough, and formed with an intersecting frusto-conical socket 97 in which is received a correspondingly-shaped valve head Q3 formed with a passage 9S therethrough. A stem lili) is connected to the valve head 93 and may be provided with an operating handle lei read-ily accessible to the operator, as shown in Fig. 6.

An escape valve H52 provides a controlled passage from the interior of the bag 58 to the chamber "it through the port lee and the port lll. A valve member H355 controls such flow, being reciprccably mounted in the case 4t2 and being formed with a passage it registrable in one position, with the port itil. A port HB1 places the lower end oi the valve member M5 in open communication with the circumambient medium in the chamber le, and the upper end of said valve member is always in open communication with the gas in the bag 6in, A spring I e8 tends to hold the valve member tile in the position illustrated in Fig. 6.

Means must be provided for floodingthe chainber Ee and its extension 3e, since the pressures on opposite sides of the hatch 32 must be substantially equalized before the hatch can be opened. In Figs. 1 and 2 I have illustrated a pipe l Ue leadingrfrom the `exterior of the vessel to the .chamber .29, .a valve I le, accessible from within the room l25, provided to control iiow through vsaid pipe.

Although, once the chamber 29, 3i) is flooded and the hatch 32 is removed, the buoy 31 will tend to float out of the chamber 30, I prefer to provide mechanical means for positively ejecting the buoy. Such means comprises a yoke III, illustrated in Figs. 1 and 10, immediately sub- .'iaeent the iiange 59, and a push rod H2 operatively associated therewith. As is clearly shown, said push rod is provided with rack teeth I I3 and is mounted to slide through a gear box H4 in which is positioned a pinion H5 carried on a shaft Ht rotatable by a hand wheel li'l accessible from within the room 25.

In case of an emergency, the door 23 is opened and the handle ll is rotated through 90 to place the pressure-responsive element 32 in control of the liquid column in the pipe 813. Immediately, the pressure of air upon the pressureresponsive element 82 will be communicated to the head 92. Since the effective area of the head Si?. is greater than the eiective area of the head 53, and since the pressures existing in the chamber e! and within the bag 66 are equal, the valve e! will be raised to bring the passage 94 into registry with the conduit 88. It will be noted that the passage 94 is small, so that air iiow, even though the pressure within the reservoir 52 is very high, will be gradual. Immediately after opening valve 83, the door 23 is closed and sealed and the valve liti is opened to flood the chamber 29, 3i). As soon as the pressure within the chamber 29, 36 substantially equals the pressure upon the outer surface of the hatch 32, the hatch 32 is removed by standard operating means and the hand wheel lll is operated to eject the buoy 3?. As the buoy 3l leaves the chamber Se, the spring 'iii forces the bracket 'i8 upwardly, thereby expanding the shield which, until that time, has acted to prevent the bag t6 from scraping against the surfaces of the chamber 3i).

Meantime, air is owing into the bag (it. The pressure now impressed upon the element 82 is the pressure of the surrounding water; so that air will continue to flow into the bag et from the reservoir 52 until the pressure within the bag somewhat exceeds the outside water pressure, whereupon the effective pressure upon the head 93 will exceed `the effective pressure upon the head 92 to return the valve 9i to the position of Fig. 6. While the differential between pressure within the bag and the water pressure may be any reasonable predetermined amount, I prefer to proportion the parts so that the valve SI will be returned to the position illustrated in Fig. 6 when the pressure within the bag 66 exceeds the water pressure by approximately eight pounds per square inch.

The bag 6e is so proportioned that it will readily lift the weight of the amount of conduit trl carried aboard the vessel. If desired, and in order to assist the rise of the buoy, the motor 35 may be operated during the rise of the buoy to rotate the reel 33 te feed the conduit to the buoy.

Gbvio'usly, if the vessel rests upen the bottom at va level such that the water pressure is two hundred pounds per square inch, and if a pressure of two hundred and eight pounds per square inch is charged into the bag, the pressure upon the bag is only eight pounds per square inch. if the buoy were permitted to rise to the surface, however, without valving air out of the `bag, the rupturing pressure of the gas within the bag would become one hundred and ninety-three pounds per square inch; and it is impractical to provide a bag made of material capable of withstanding such a rupturing pressure. It is for this reason that I have provided the valve mechanism |2|9.

As has been stated, the spring |38 tends to hold the valve member |35 in the position of Fig. 6, as does also the pressure of the circumambient medium. The pressure within the bag, however, tends to move the valve member |35 in a direction to bring the passage |43 into registry with the port |34. l prefer so to proportion the spring |38 that the valve will be moved to exhaust position when the pressure within the bag exceeds the pressure of the circumambient medium by a value slightly greater than the pressure differential which will close the valve 9|; for instance, ten pounds. Thus, if we again assume that the buoy is released at a point at which the water pressure is two hundred pounds per square inch, it will be seen that the valve |35 remains in closed position until after the valve 3| is closed. As the buoy rises, the water pressure will decrease. If gas has been charged into the bag to a pressure of two hundred and eight pounds per square inch, the valve |33 will remain closed until the buoy has reached a position at which the circumambient pressure is ninety-eight pounds, whereupon the valve |35 will open to discharge some air from the bag. If it be assumed that everything is perfectly 'air-tight, it will be clear that the valve 9i will not again be opened as the buoy rises, but that the valve |35 will be periodically opened, or that it may remain open throughout the rise of the buoy, to prevent the pressure differential between the inside and the outside of the bag 66 from rising beyond ten pounds per square inch; so that, when the buoy reaches the surface, the pressure within the bag will be twenty-rive pounds per square inch.

However, if leakage should occur, so that the pressure differential between the inside and the outside of the bag should drop to a value less than eight pounds per square inch, the valve 3| will again be opened to replenish the supply of air within the bag and to raise the pressure differential again to the eight pound value for which the valve 3| is set.

Obviously, the buoy 3l may carry any kind of signalling devices, such as lights, bells, whistles, or radio broadcasting aerials; but the particular details of such signalling mechanisms form no part of the present invention. Once the buoy is located, however, by a rescue ship, which may be provided with 'a conduit similar to the conduit 34, that conduit may be connected, by the rescue ship, to the head 5|; thereby establishing a Contact with the disabled vessel through which air may be pumped to the vessel, through which telephone communication is established, and through which electric power may be conducted to the disabled vessel.

In a second water-tight compartment I I8 there is located a reel I upon which is wound a cable |23. Within a cylindrical, vertical extension |2| of the chamber I3, there is positioned an escape car |24. The extension |2| opens at |22 through an upper Wall of the vessel, and the opening |22 is closed by a hatch |23 of standard construction.

The car |24 is provided with an exit opening |25 in its upper end, closed by a hatch |26 of standard construction and operable from either inside the car or outside the car; and with an entrance opening I2'| in its lower portion, provided with a hatch |28 of standard construction operable either from the inside or the outside of the car. The car may be provided with seats |29, if desired.

Projecting downwardly below the port |2'l is a spider |35 terminating in a collar |3I, or the like, to which is securely fastened an end of the cable |28.

The car |24 and the compartment extension |2| are formed with cooperating surfaces providing a water-tight joint |32, the details of which are illustrated in Fig. 11. As there shown, the compartment wall is formed to provide an upwardly facing annular shoulder |33 bounded at its inner edge by a flange |34. A compressible washer |35 may be positioned in the channel |33; and the upper portion of the car |24 is formed to provide a downwardly facing channel |36 receiving the upper edge of the flange |34 and a downwardly facing lip |31 adapted to engage and compress the washer |35. It will be obvious that, when the car |24 is pulled tightly down against the seal |32, these cooperating surfaces will prevent the iiow of water into the lower portions of the compartment IIS, |2|.

A door |38 provides access from the room 25 into the compartment ||8, and a platform |33 is located immediately below that door, providing a support for a person seeking entrance to the car |24. A conduit |40 leads from the outside of the vessel and communicates with a pipe |4I, controlled by a valve |42, and leading into the chamber |43 between the seal |32 and the hatch |23. The conduit |40 also communicates with a pipe |44 controlled by a valve |45 and leading into the compartment H8. The door |38, valve |42, and valve |45 are all accessible from within the room 25.

When it is desired to use the escape car, the space |43 is ooded by opening the valve |42, and the hatch |23' is thereupon removed. The door |38 and the hatch |28 are now opened and one or more men crawl into the escape car and lock the hatch |28. The valve |45 is now opened to flood the compartment ||8, |2|; and as soon as that compartment is flooded, the escape car |24 will float out of the compartment and to the surface. Assuming the presence of a rescue ship, the hatch |26 is removed, the passengers leave the car, and the hatch |26 is again secured. The crew aboard the disabled vessel is now notied by telephone that the car is ready for its return trip, and the motor |46, connected to the reel I I9 through a reduction gear |41, is operated to drive the reel |I9 to haul in the cable |20. As the car reaches the vessel, it is necessarily centered by the cable upon the opening |22, and

vis pulled into sealing engagement with the seal |32. Thereupon the door |38 is opened, whereby the compartment 2| will be emptied down to the level of the bottom of the door. True, a certain amount of water will thereby be discharged into the room 25; but it will be a relatively small amount, since all of the water below the door |38 will be retained in the compartment IIS.

Of course, this partial draining of the compartment |2| will create an enormous pressure diiferential which will hold the car |24 in sealing engagement with the washer |35.

This operation is repeated until all crew members have escaped from the disabled vessel.

I claim as my invention:

1. A distress signalling mechanism for submarines comprising' a collapsible buoy adapted to be carried on a vessel in collapsed condition, a reservoir containing a compressed gas, said reservoir being carried on said buoy, conduit means providing communication between said reservoir and the interior of said buoy, valve means controlling flow through said conduit means and comprising an element having a surface subject to the pressure currently existing in the interior of said buoy and having a larger opposing surface subject to the current pressure of the circumambient medium, said element being movable, under the joint eiect of a pressure within the buoy exceeding the pressure of such medium by less than a predetermined value, to open said valve means to permit ow through said conduit, and movable to close said valve means Whenever the pressure within said buoy exceeds the pressure of said medium by more than such predetermined value, and a second valve means controlling communication between the interior of said buoy and the circumambient medium, and comprising an element having a surface subject to the pressure currently existing in the interior of said buoy and an opposing surface subject to the current pressure of such circumambient medium, and movable under the joint effect of a pressure within the buoy exceeding the pressure of such medium by more than a predetermined value, to open said second valve means, but movable to close said second Valve means whenever the pressure within said buoy exceeds the pressure of such medium by less than such last-mentioned predetermined value.

2. A distress signalling mechanism for submarines comprising a collapsible buoy adapted to be carried on a vessel in collapsed condition, a reservoir containing a compressed gas, said reservoir being carried on said buoy, conduit means providing communication between said reservoir and the interior of said buoy, valve means controlling flow through said conduit means and comprising an element having a surface subject to the pressure currently existing in the interior of said buoy and having a larger opposing surface subject to the current pressure of the circumambient medium, said element being movable, under the joint effect of a pressure within the buoy exceeding the pressure of such medium by less than a predetermined value, to open said valve means to permit ow through said conduit, and movable to close said valve means whenever the pressure within said buoy exceeds the pressure of said medium by more than such predetermined value, and a second valve means controlling communication between the interior of said buoy and the circumambient medium, comprising an element having a surface subject to the pressure currently existing in the interior of said buoy and an opposing surface subject to the current pressure of such circumambient medium, and movable, under the joint effect of a pressure Within the buoy exceeding the pressure of such medium by more than a predetermined value higher than said first-mentioned predetermined value, to open said second valve means, but movable to close said second valve means Whenever the pressure within said buoy exceeds the pressure of such medium by less than such lastmentioned predetermined value.

3. A distress signalling mechanism for submarines comprising a collapsible buoy adapted to be carried on a Vessel in collapsed condition, a reservoir containing a compressed gas, conduit means providing communication between said reservoir and the interior of said buoy, valve means controlling ow through said conduit means and comprising an element having a surface subject to the pressure currently existing in the interior of said buoy and having a larger opposing surface subject to the current pressure of the circumambient medium, said elementl being movable, under the joint eiect of a pressure Within the buoy exceeding the pressure of such medium by less than a predetermined value, to open said valve means to permit flow through said conduit, and movable to close said valve means Whenever the pressure Within said buoy exceeds the pressure of said medium by more than such predetermined value, and a second valve means controlling communication between the interior of said buoy and the circumambient medium, and comprising an element having a surface subject to the pressure currently existing in the interior of said buoy and an opposing surface subject to the current pressure of such circumambient medium, means biasing said second valve means toward closed position, and said element being movable, under the joint effect of a pressure within the buoy exceeding the pressure of said medium by more than a predetermined value, to open said second valve means, but movable to close said second valve means whenever the pressure within said buoy exceeds the pressure of such medium by less than such last-mentioned predetermined value.

CARROLL D. PLEAK.

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