US2931534A - Automatic emergency drain mechanisms for floating roofs - Google Patents

Description

April 5, 1960 J. H. WIGGINS 2,931,534

AUTOMATIC EMERGENCY DRAIN MECHANISMS FOR FLOATING ROOFS Filed April 7, 1958 2 Sheets-Sheet l s 0 m R m W 0 g I T m I W W H W H al 1 m z -EMA m 2. y 4

April 5, 1960 J. H. -VVIGGINS 2,931,534

AUTOMATIC E MERGENCY DRAIN MECHANISMS FOR FLOATING ROOFS Filed April 7, 1958 2 Sheets-Sheet 2 l am KNVENTOR. John H Wiggins g Sim @4 4 M 2;

United States Patent AUTOMATIC EMERGENCY DRAIN MECHANISMS FOR FLOATING ROOFS John H. Wiggins, Menlo Park, Calif. Application April 7, 1958, Serial No. 726,810 12 Claims. Cl. 220-26) The present invention relates to floating roots for field storage tanks, and more particularly to automatic emergency drain mechanism for such floating roofs.

In a field storage tank for crude petroleum, gasoline and other light hydrocarbon liquids, it is desirable to support the floating roof thereof within 1 to 3 feet'of the bottom wall of the tank, when substantially all of the liquid is drained from the tank; and to this end, the floating roof carries foot structure that directly engages the bottom wall of the tank for supporting the roof in its non-floating position. The floating roof is also normally provided with regular drain mechanism and with emergency drain mechanism, both for the purpose of removing water from the top of the roof resulting from precipitation thereupon, since the top of the storage tank is open to the weather. The regular drain mechafnism ordinarily drains the water from the roof through the liquid stored in the tank and thence to' the outside;

'while the emergency drain mechanism ordinarily drains the water from the roof directly into the liquid stored in the tank.

In a conventional arrangement, the emergency drain mechanism is of the syphon type and includes a water leg that must be maintained at a length in the general range to '9 feet in order to prevent the back-flow therethrough of the liquid stored in the tank whenthe roof is moved into itsnon-floating position. Accordingly, a deep sump is provided in thebottom wall of the tank to receive the emergency drain mechanism, when the roof is in its non-floating position.

While this conventional arrangement is generally satisfactory, it is subject to the criticism that it is expensive to manufacture; and moreover in cold climates, it is subject to the additional criticism that water accumulating in the sump sometimes freezes therein causing damage to the emergency drain mechanism incident to movement of the roof between its floating and non-floating positions.

Accordingly, it is a general object of the present invention to provide in a floating roof fora liquid storage tank, improved emergency drain mechanism that does not require the provision of the usual cooperating sump in the bottom wall of the associated storage tank to receive the emergency drain mechanism when the floating roof is in its lower non-floating position.

Another object of the invention is to provide floating roof drain mechanism of the character noted, that incorporates an improved arrangement for effecting draining of water from the roof when the roof is in its floating position and for preventing back-flow of liquid from the associated tank when the roof is moved into its nonfloating position. 1

A further object of the invention is to provide an auto- 2,931,534 Patented Apr. 5, 1960 ice Further features of the invention pertain to the par ticular arrangement of the elements of the floating roof automatic drain mechanism, whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification, taken in connection with the accompanying drawings, in which:

Figure 1 is a vertical sectional view taken through a storage tank provided with a floating roof incorporating automatic emergency drain mechanism embodying the present invention;

Fig. 2 is a greatly enlarged fragmentary elevational view, partly in section, of the drain mechanism shown in Fig. 1;

Fig. 3 is a greatly enlarged plan view of the drain mechanism shown in Fig. 2;

matic drain mechanism of the character described, an

ing roof.

Fig. 4 is an enlarged fragmentary side elevational view, partly in section, of the drain mechanism, illustrating the positions of the elements thereof when the associated roof is in its floating position; 1

Fig. 5 is another enlarged fragmentary side elevational view, partly in section, of the drain mechanism, illustrating the positions of the elements thereof when the associated roof is in its non-floating position; and

Fig. 6 is an enlarged fragmentary side elevational view, partly in section, of a modified form of the drain mechanism.

Referring now to Fig. 1 of the drawings, the field storage tank 10 there illustrated is especially adapated for use in the storage of crude petroleum, gasoline and other light hydrocarbon liquids, and is provided with a floating roof'20 incorporating drain mechanism 30 embodying' the features of the present invention. More particularly, the storage tank 10 comprises a substantially tubular side wall 11 provided with an open top surrounded by an outwardly and downwardly directed marginal flange 12, as well as a substantially circular bottom wall 13 that may be directly carried upon the earth. Also, a shallow sump 14 is provided in the bottom wall 13 and connected by a drain conduit 15 to exterior piping, not shown; which drain conduitlS includes a manual valve 15 that is normally closed. 1

The roof 20 essentially comprises an outer substan tially annular pontoon 21 that is adapted to float upon the liquid stored in the tank 10, and a substantially circular deck 22 arranged within the pontoon 21 and sealed thereto. Normally, the deck 22 is formed of a series of segmental sheets suitably welded together and to the pontoon 21 so as to provide a composite imperforate structure. The pontoon 21 is spaced somewhat inwardly with respect to the adjacent side wall 11 of the tank 10 and an annular seal 23 is arranged therebetween. The seal 23 may be of any suitable construction and is normally carried by the outer surface of the pontoon 21 and arranged in sliding sealed engagement with the adjacent inner surface of the side wall '11. Further, the pontoon '21 carries foot structure, including a position of the roof 20. On the other hand,.when"substantially all of the liquid is drained from the tank 10,

the roof 20 is moved .toward the bottom wall 13 pfthe tank and ultimately the feet 24 depending from the roof engage the bottom wall 13 and support the roof 20 when the amount of liquid stored in the tank 10 is inadequate to float the roof 20.

Referring now to Figs. 2 and 3, the drain mechanism essentially comprises an upstanding elongated tube 31 projecting through an opening 22a provided in the deck 22 adjacent to the central portion thereof. A short upstanding annular collar 32 is carried by the top of the deck 22 in surrounding relation with respect to the deck opening 22a and sealed to the deck 22; and the upper end of the collar 32 is threaded, as indicated at 32a, so as removably to receive a cooperating cap 33 having a centrally disposed opening 33a therein through which the tube. 31 projects. In the arrangement, a packing gland or seal is provided mutually between the collar 32, the -cap 33 and the tube 31; which seal comprises a bearing ring 34 disposed internally of the collar 32, a bearing ring 35 disposed internally of the cap 33 and a sealing ring or gasket 36 arranged between the bearing rings 34 and 35. The ring 34 is sealed to the collar 32, and the "ring 35 is sealed to the cap 33; while the gasket 36 is maintained in compression between the bearing rings 34 and 35 and into distended'condition in frictional engagement with the adjacent outer surface of the tube 31. For example, the gasket 36 may comprise an annular ring formed of soft synthetic rubber, such as neoprene.

In view of the foregoing, it will be understood that the tube 31 projects through the deck opening 22a, the

.collar 32 and the cap opening 33, as well as the bearing- rings 34 and 35 and the ring gasket 36; whereby the tube" 31 is capable of vertical sliding movement with respect to the deck 22 and in sealed relation with the collar 32. The extremeupper end of the tube 31 car- :ries anumber of outwardly directed pins 37 that serve ..as stops that cooperate with the cap 33 to limit the -movement of the tube 31 downwardly with respect to the collar 32.

The extreme lower end of the tube 31 carries a substantially pan-like structure 38 including a bottom wall 39 and an upwardly directed side wall 40, and a number of radially extending and angularly spacedapart arms 41 secured between the extreme lower end of the-,tube 31 and the upper portion of the side wall of the pan structure 38. Also, a weight that may comprise a plate-like element 42 is secured to the bottom wall 39 ofthe pan structure 38 so as to bias the pan structure 38, and also the tube 31, downwardly by the action of .gravity. In the arrangement, the side wall 40 of the pan 38 extends upwardly above the extreme lower end of the tube 31; whereby the pan structure 38 communi 'cates with the lower end of the tube 31 and opens into the liquid stored in the tank 10, for a purpose more fully explained below.

Also a short upstanding annular ring 43 is secured ,.to the top surface of the deck 22 in surrounding relation with the collar 32; which ring 42 is sealed to the deck 22 and has a height somewhat less than that of the collar 32 so as to provide an annular space 44 therebetween that is open to the outside for the accumulation of drain water therein. The ring 43 comprises a portion of a regular drain mechanism for the floating roof 20 that further comprises a flexible drain hose 45 extending between the roof 20 and the lower portion of the tank 10.

More particularly, the upper end of the drain hose 45 pro ects through an associated opening provided in the deck 22 and terminates in an opening provided in the ring 43, the extreme upper end of the drain hose 45 'being secured and sealed in an opening provided in the side of the ring 43. The extreme lower end of the drain hose 45 is secured to a drain fixture 46 arranged in the lower portion of the side wall 11 adjacent to the bottom wall 13,. which drain fixture 46 includes a manually operable valve 47.

a In the arrangement, the drain hose 45 extends between the annular space '44 through the" liquid stored 'in the tank '11 to the drain fixture 46, and the manual valve 47 is normally retained in its closed position so as to prevent the escape of the liquid stored in the tank 10 in the event of a puncture in the drain hose 45. However, the drain valve 47 may be opened to accommodate the draining of water from the floating roof 20 in an obvious manner; and in this event, the water accumulating upon the deck 22 flows over the top of the ring 43 into the annular space 44 and thence via the flexible drain hose 45 into the drain fixture 46 and thence via' the open drain valve 47 to the exterior.

Considering now in greater detail the construction and arrangement of the emergency drain mechanism 30 that includes the slidably mounted tube 31, particular reference is made to Figs. 4 and 5. Specifically, the tube 31 is moved into its extreme lower position with respect to the deck 22, as shown in Fig. 4, by the weight 42, when the roof 20 is in its floating position; on the other hand, when the roof 20 is in its non-floating position, the weight '42 engages the bottom wall 13 of the tank 10, thereby moving the tube 31 upwardly into its extreme upper position with respect to the deck 22, as shown in Fig. 5. Of course, when the roof 20 is again floated, the elements of the drain mechanism 30 are returned from the positions of Fig. 5 into the positions of Fig. 4. When the mechanism 30 occupies its draining position of Fig. 4, with the roof 20 in its floating position, the water accumulating upon the deck 22 rises sufficiently high so that it spills over the cap 33 into the extreme upper end of the tube 31 and flows ultimately into the pan structure 38 and therefrom into the liquid stored in the tank 10. The water being somewhat heavier than the hydrocarbon liquid normally stored in the tank 10 settles into the sump 14 and can be ultimately drained therefrom via the drain conduit 15 when the drain valve 16 is operated into its open position. On the other hand, when the mechanism 30 occupies its non-draining position of Fig. 5, with the roof 20 in its non-floating position, the upper end of the tube 31 is projected sufliciently above the deck 22 to prevent entry of the water accumulating upon the deck 22 into the tube 31.

In a constructional example of the drain -mecha-' nism 30.'and as illustrated inFigs. 4 and 5, the distances indicated by the letters A," B, C and D may be respectively: about 3 to 4", about 18 to 24", about 6 to 9 feet, and about 12'. More particularly, the top of the cap 33 may be disposed above the top of the deck 22 (the distance A) about 3 to 4"; the vertical distance between the top of the pan 38 and the top of the deck 22 with the roof 20 in its non-floating position (the distance B) may be about 18 to 24"; the vertical distance between the top of the pan 38 and the top of the tube 31 (the distance C) may be about 6 to 9 feet; and the vertical distance between the top of the deck 22 and the normal liquid level in the tank 10 with the roof 20 in its floating position (the distance D) may be about 12". In Fig. 4, the normal liquid level in the tank 10 with the roof 20 in its floating position is indicated by the broken line 50; which normal liquid level normally occurs in the seal 23 and suitably below the top of the pontoon 21.

In the operation of the drain mechanism 30, when the roof 20 is moved toward a non-floating position, there is a tendency for the liquid in the tank 10 to back-flow through the tube 31 onto the top of the deck 22; which would be the consequence of shortening the distance between the top of the pan structure 38 and the bottom of the deck 22, if the tube 31 were not projected above the deck 22, as the roof 20 is moved into its non-floating position. However, in the present construction, there is no backrflow of the liquid through the tube 31 because of the projection thereof above the deck 22 as the roof 20 is moved into its non-floating position following-engagement of the weight 42 with the bottom wall 13 of the' tank 10. Moreover, since the weight 42 and the pan structure 38 are moved toward the bottom of'the deck this undesirable expense in the construction of the tank 1 10. Of course, it will be understood that when the feet 24 directly engage the bottom wall 13 of the roof 20 in its non-floating position; the deck 22 is normally about 2% to 3 feet above the bottom wall 13, so that there is adequate space between the deck 22 and the bottom wall 13 to accommodate the pan 38 and the weight 42.

Referring now to Fig. 6, the modified form of the emergency drain mechanism 60 there illustrated is fundamentally of the same construction as the emergency drain mechanism 30 above described; however, in this construction, the tube that projects through the deck 22 comprises a rigid intermediate section 61, an upper flexible section 62 and a lower flexible section 63. In the arrangement, the intermediate section 61 extends through an opening provided in the deck 22 and is suitably secured in place, as by welding, as indicated at 64, so that the intermediate section 61 is sealed to the deck 22. The upper section 62 essentially comprises a suitable length of flexible hose; and likewise, the lower section 63 essentially comprises a suitable length of flexible hose. Specifically, the hose sections 62 and 63 may be formed of synthetic rubber, such as neoprene.

Further, the mechanism 60 comprises the elongated upstanding rod 65 that is mounted for vertical sliding movement in the collar 66 and in sealed relation therewith. The lower end of the rod 65 carries the pan 68 that is arranged in opencommunication with the liquid stored in the tank 10. Specifically, a tubular fixture 69 is arranged in the lower portion of the cylindrical side wall of the pan 68, and the outer end thereof is secured to the adjacent lower end of the hose 63; and the upper end of the rod 65 carries a bracket 70 that is connected by an associated flexible element 71 to the adjacent outer end of the hose 62, the element 71 being formed of steel cable, chain, etc. Further, the upper portion of the rod 65 carries a stop pin 72 that cooperates with the cap 73 that is carried by the top of the collar 66 so as to limit the downward movement of the rod 65. Of course, the collar 66 is surrounded by the ring 43 that communicates with the regular drain hose 45, in the manner previously explained.

Considering now the general mode of operation of the emergency drain mechanism 60, it will be understood that when the roof '20 is in its floating position, the rod 65 is biased into its lower position by the associated weight 74 that is carried by the pan structure 68 so that the stop 72 cooperates with the cap 73 eflecting movement of the bracket 70 into its lower position. At this time, the pan structure 68 occupies its lower positionso that the hose 63 is extended between the pan structure 68 and the intermediate tubular section 61, and the bracket 70 lowers the outer end of the hose 62 to a position disposed substantially flush with the top of the cap '73. At this time, when the regular drain conduit 45 is closed, any water accumulatingupon the deck 22 can, upon rising to a suitable height, enter into the outer end of the hose 62 andflow therethrough and thence through the intermediate tubular section 61 and the hose 63 into the pan 68. From the pan 63, the water overflows into the liquid stored in the tank 10, in the manner previously explained.

When the roof 20 is moved into its non-floating position, the weight 74 engages the bottom wall 13 of the tank 10 moving the pan structure 68 and the rigidly connected rod upwardly, and ultimately into its upper position, as the feet 24 carried by the roof 20 engage the bottom wall 13 of the tank 11. As the rod 65 is moved upwardly, the bracket elevates the outer end of the hose 62 through the connecting element 71, thereby :substantially to elevate the outer end .of the hose 62 above :the deck 22, so as to prevent the shack-flow of the liquid from the tank 10 through the tube include ing the sections 61, 62 and 63. In other words, as the pan structure 68 is moved upwardly, as the roof 20 is moved into its non-floating position, the rod 65 is moved upwardly so that the upper hose section 62 is lengthened, as the lower hose section 63 is shortened; whereby the overall vertical height of the tube, including the. sections 61, 62 and 63 remains substantially constant, regardless of the position of the floating roof 20. Accordingly, it will be understood that the mechanism 60 is moved into its draining position when the roof 20 is in its floating position, and the mechanism 60 is moved into its nondraining position when the roof 20 is moved into its non-floating position.

In view of the foregoing, it is apparent that there has been provided an emergency drain mechanism of improved and simplified construction and arrangement, that is operative to effect draining of water from the top of the floating roof, in the event that such draining is not effected by the regular drain mechanism when the roof occupies its floating position; which emergency drain mechanism insures that there is no back-flow of the liquid from the storage tank incident to movement of the roof into its non-floating position.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appendedv claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a roof ofthe floating type for a liquid storage tank, and adapted to float upon the liquid stored in the tank, so that said roof rises and falls with variations in the liquid level in the tank, said roof including a deck positioned below the top thereof, whereby precipitation accumulates on the top of said deck, and wherein said roof is supported in a non-floating position in the lower portion of the tank by foot structure engaging the bottom wall thereof when the liquid is drained therefrom; the drain mechanism combination comprisinga tube carried by said deck and arranged in an opening provided therein and projecting through said deck opening and sealed to said deck, whereby the upper and lower ends of said tube are respectively disposed above and below said deck, means responsive to movement of said roof into its floating position for moving the upper end of said tube to a lower position disposed adjacent to the top of said deck and for moving the lower end of said tube ma lower position disposed well belowsaid deck, means responsive to movement of said roof into its non-floating position for moving the upper end of said tube to an upper position disposed well above the top of said deck and for moving the lower end of said tube to an upper position disposed adjacent to said deck, the vertical distance between the ends of said tube being maintained substantially greater than the distance betweensaid roof in its non-floating position and the bottom of the tank, the upper end of said tube in its lower position accommodating the draining thereinto of water accumulating on the top of said deck when said roof is in its floating position and the upper end of said tube in its upper position preventing the back-flow therethrough of liquid from the tank as said roof is moved into its non-floating position, and means including a member communicating with the lower end of said tube and extending upwardly thereabove and opening into the liquid stored in thetank for controlling the How of the water in said tube into the liquid stored in the tank.

2. The floating roof drain mechanism .set forth inclaim 1, wherein the length of said tube between theupper and lower ends thereof is several times the dis-- tance between said roof in its non-floating position and the bottom of the tank.

3. The floating roof drain mechanism set forth in.

1 ela'iin 1, iwhereinfsaid tube are one-piece metalfcom structionand is 'slidablyjmounted in said deck opening in sealed relationwith'said deck. q I

4. In a roof of the floating type for a'liquid storage tank, and adapted to float upon the liquid stored in the tank, so that'said roof rises and falls with variations in the liquid level in the tank, said roof including a deck positioned below the top thereof, whereby precipitation accumulates on the top of said deck, and wherein said roof is supported in a non-floating position in the lower portion of the tank by foot structure engaging the bottom wall thereof when the liquid is drained therefromrthe drain mechanism combination comprising'a tube carried by said deck and arranged in an opening provided therein and projecting through said deck opening and sealed to said deck, whereby the upper and lower ends of said tube arerespectively disposed above and below said deck, means responsive to movement of said roof into its floating position for moving the upper end of said tube to a lower position disposed-adjacent to the top of said deck and for moving the lower end of said tube to a lower position disposed well below said deck, means responsive to movement of said roof into itsnon-flo'ating position for moving the upper end of said tube to an upper position disposed well above the top of said deck and for moving the lower end of said tube to an upper position disposed adjacent to said deck, the vertical distance between the ends of said tube being maintained substantially greater than the distance between said roof in its non-floating position and the bottom of the tank, the upper end of said tube in its lower position accommodating the draining thereinto of water accumulating on the top of said deck when said roof is in its floating position and the upper end of said tube in its upper position preventing the back-flow therethrough of liquid from the tank as said roof is moved into its nonfloating position, and means including a substantially cup-shaped member carried by the lower end of said tube for controlling the 'flowof the water therefrom into the liquid stored in the tank, said member being movable with the lower end of said tube and communicating therewith and provided with a rim projecting upwardly above the lower end of said tube and opening into the liquid stored in the tank.

5. In a roof of the floating type for a liquid storage tank, and adapted to float upon the liquid stored in the tank, so that said roof rises and falls with variations in the liquid level in the tank, said roof including a deck positioned'below the top thereof, whereby precipitation accumulates on the top of said deck, and wherein said roof is supportedin a non-floating position in the lower portion of the tank by foot structure engaging the bottom wall thereof when the liquid is drained therefrom; the drain mechanism combination comprising an elon- "gated upstanding tube carried by said deck and projecting through an opening provided therein, means mounting "said tube for sliding movements in said opening and in sealed relation with said deck, means responsive to movement of said roof into its floating position for moving said tube into a lower position with respect to said deck, means responsive to movement of said roof into its nonfloating position for moving said tube into an upper position with respect to said deck, the length of said tube between the upper and lower ends thereof being substantially greater than the distance between said roof in its non-floating position and the bottom of the tank, the upper end of said tube being positioned adjacent to the topofsaid deck when said tube occupies its lower position so as to accommodate the draining thereinto of water accumulating on the top of said deck when said roof is in its floating position and the upper end of said tube being positioned well above the top of said deck when said tube occupies its'upper position so as to prevent the back-flow therethrough of liquid from the tank as said roof is moved into its non-floating position, and means including a member-communicating with the lower end again-est of said tube' and eittending upwardlytnereatove and spaning-into the liquid 'sto'red in'the tank for controlling '-flow'- of the water in said tube into the liquid stored in the tank.

' 6. 1m a'roofof the floating type for a liquid'storage tank, and adapted to float upon the liquid stored in the tank, so that said roof rises and falls with variations in the liquid' level in the tank, said roof including a deck po'sitionedbelow the top thereof, whereby precipitation accumulates on the top of said deck, and wherein'said roof is supported in a non-floating position in the lower portion of the tank by foot structure engaging the bottom wall thereof when the liquid is drained therefrom; the drain mechanism combination comprising a short upstanding collar carried by said deck and sealed there- 'to and surrounding an opening provided in said deck, the upper end of said collar being disposed below the top of said roof, an elongated upstanding tube arranged within said' collar and carried thereby and projecting through said'deck' opening, means mounting said tube for sliding movements in said collar and in sealed relation therewith, means responsive to movement of said roof into its floating position for moving said tube into a lower position with respect to said deck, means responsive to movement of said roof into its non-floating position for moving' said tube into an upper position with respect to said deck, the length of said tube between the upper and lower ends thereof being substantially-greater than the distancebetween said roof in its non-floating position and the bottom of the tank, the upper end of said tube being positioned adjacent to the top of said deck when said tube occupies its lower position so as to accommodate the draining thereinto of water accumulating on the top of said deck when said roof is in its floating position and the upper end of said tube being positioned well above the top of said deck when said tube occupies'its upper position so as to prevent the back-flow therethrough of liquid from the tank as said roof is moved into its nonfloating position, and means including a member communicating with the lower end of said tube and extending upwardly thereabove and opening into the liquid stored in the tank for controlling the flow of the water in said tube into the liquid stored in the tank.

7. In a roof of the floating type for a liquid storage tank, and adapted to float upon the liquid stored in the tank, so that said roof rises and falls with variations in the liquid level in the tank, said roof including a deck positioned below the top thereof, whereby precipitation accumulates on the top of said deck, and wherein said roof is supported in a non-floating position in the lower portion of the tank by foot structure engaging the bottom wall thereof when the liquid is drained therefrom, the

drain mechanism combination comprising an elongated upstanding tube carried by said deck and projecting through'an opening provided therein, means mounting said tube for sliding movements in said opening and in sealed relation with said deck, a weight carried by the lower and of said tube below said deck, said weight moving said tube into a lower position with respect to said deck in response to movement of said roof into a floating position and the lower end of said tube cooperating with the bottom of the tank to move said tube to-an upper position with respect to said deck in response to movement of said roof into a non-floating position, the length of said tube between the upper and lower ends thereof being substantially greater than thedistance between said roof in its non-floating position and the bottom of the tank, the upper end of said tube being positioned adjacent to the top of said deck when said tube occupies its lower position as as to accommodate thedraining thereinto of water accumulating on the top of said' deck when said roof is in its-floating position and the upper end of said tube being positioned well above the top of 'said deck when said tube occupies its upper position so as to prevent the'back-flow therethrough of liquidfro'm asamsa 9 the tank as said roof is moved into its non-floating position, and means including a member communicating with the lower end of said tube and extending upwardly thereabove and opening into the liquid stored in the tank for controlling the flow of the water in said tube into the liquid stored in the tank.

8. The floating roof drain mechanism set forth in claim 1, wherein said tube comprises an intermediate section rigidly secured to said deck in said deck opening and also flexible upper and lower sections respectively disposed above and below said deck and respectively sealed to the upper and lower ends of said intermediate section.

9. In a roof of the floating type for a liquid storage tank, and adapted to float upon the liquid stored in the tank, so that said roof rises and falls with variations in the liquid level in the tank, said roof including a deck positioned below the top thereof, whereby precipitation accumlates on the top of said deck, and wherein said roof is supported in a non-floating position in the lower portion of the tank by foot structure engaging the bottom wall thereof when the liquid is drained therefrom; the drain mechanism combination comprising a short tubular element carried by said deck and arranged in an opening provided therein and projecting through said deck opening and sealed to said deck, a first tube disposed above said deck and sealed at one end thereof to the upper end of said tubular element, means mounting the other end of said first tube for vertical movement toward and awayfrom said deck, a second tube disposed below said deck and sealed at one end thereof to the lower end of said tubular element, means mounting the other end of said second tube for vertical movement toward and awayfrom said deck, means responsive to movement of said roof into its floating position for moving the other end of said first tube to a lower position disposed adjacent to the top of said deck and for moving the other end of said second tube to a lower position disposed well below said deck, means responsive to movement of said roof into its non-floating position for moving the other end of said first tube to an upper position disposed well above the top of said deck and for moving the other end of said second tube to an upper position disposed adjacent to said deck, the vertical distance between the other end of said first tube and the other end of said second tube being maintained substantially greater than the distance between said roof in its non-floating position and the bottom of the tank, the other end of said first tube in its lower position accommodating the draining thereinto of water accumulating on the top of said deck when said roof is in its floating position and the other end of said first tube in its upper position preventing the backflow therethrough of liquid from the tank as said roof is moved into its non-floating position, and means including a member communicating with the other end of said second tube and extending upwardly thereabove and opening into the liquid stored in the tank for controlling the flow of the water in said second tube into the liquid stored in the tank.

10. The floating roof drain mechanism set forth in claim 9, wherein each of said first and second tubes esentially comprises a flexible hose.

11. In a roof of the floating type for a liquid storage tank, and including an annular pontoon adapted to float upon the liquid stored in the tank, so that it rises and falls with variations in the liquid level, a substantially annular deck carried by said pontoon and movable therewith, said deck being sealed to said pontoon and positioned below the top thereof, whereby precipitation accumulates on the top of said deck, and foot structure depending from said roof and adapted to engage the bottom of the tank when the liquid is drained therefrom, thereby to support said roof in a non-floating position in the lower portion of the tank; the drain mechanism combination comprising a tube carried by said deck and arranged in an opening provided therein and projecting through said deck opening and sealed to said deck, whereby the upper and lower ends of said tube are re spectively disposed above and below said deck, means responsive to movement of said roof into its floating position for moving the upper end of said tube to a lower position disposed adjacent to the top of said deck and for moving the lower end of said tube to a lower position disposed well below said deck, means responsive to movement of said roof into its non-floating position for moving the upper end of said tube to an upper position disposed well above the top of said deck and for moving the lower end of said tube to an upper position disposed adjacent to said deck, the vertical distance be tween the ends of said tube being maintained substantially greater than the distance between said roof in its non-floating position and the bottom of the tank, the

upper end of said tube in its lower position accommodating the draining thereinto of water accumulating on the top of said deck when said roof is in its floating position and the upper end of said tube in its upper position preventing the back-flow therethrough of liquid from the tank as said roof is moved into its non-floating position, and means including a member communicating with the lower end of said tube and extending upwardly thereabove and opening into the liquid stored in the tank for controlling the flow of the water in said tube into the liquid stored in the tank.

12. In a roof of the floating type for a liquid storage tank, and adapted to float upon the liquid stored in the tank, so that said roof rises and falls with variations in the liquid level in the tank, said roof including a deck positioned below the top thereof, whereby precipitation accumulates on the top of said deck, and wherein said roof is supported in a non-floating position in the lower portion of the tank by foot structure engaging the bottom wall thereof when the liquid is drained therefrom; inverted siphon drain mechanism carried by said roof and comprising a tube arranged in an opening provided in said deck and sealed to said deck, said tube having an inlet disposed on the top side of said deck and an outlet disposed on the bottom side of said deck, the inlet of said tube having a draining position disposed adjacent to said deck and a non-draining position disposed well above said deck, means responsive to movement of said roof into its floating position for lowering the inlet of said tube into its draining position, and means responsive to movement of said roof into its non-floating position for raising the inlet of said tube into its non-draining position.

References Cited in the file of this patent UNITED STATES PATENTS 1,854,534 Wiggins Apr. 19, 1932

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