US3434619A

US3434619A - Floating roof seal

Info

Publication number: US3434619A
Application number: US617335A
Authority: US
Inventors: Ardell H Nelson
Original assignee: Pittsburgh Des Moines Steel Co
Current assignee: PITTSBURGH-DES MOINES Corp
Priority date: 1967-02-20
Filing date: 1967-02-20
Publication date: 1969-03-25
Anticipated expiration: 1986-03-25
Also published as: GB1195417A

Description

March 25, 1969 A. H. NELSON 3,434,619

FLOATING ROOF SEAL Filed Feb. 20, 1967 Sheet Y of e INVENTOR flrczeZZ b. Weison BYJ d )g m ATTORNEYS March 25, 1969 Filed Feb. 20. 1967 A. H NELSON 3,434,619

FLOATING ROOF SEAL Sheet 3 of 6 BY%ML1/MJ 'INVENTOR )W aZZZ'Tu.

' AITORNEYS March 25, 1969 A. H. NELSON 3,434,619

FLOATING RobF SEAL Filed Feb. 20, 1967 Sheet 4 of s llllll ll'l'l H INVENT OR BY Mm ATTORNEYS A. H. NELSON FLOATING ROOF SEAL heet 5 f 6 INVENTOR flrz/iifl/Ve/q ATTORNE March 5 1969 Filed Feb. 20, 1967 March 25, 1969 A. H. NELSON FLOATING ROOF SEAL Sheet Filed Feb. 20, 1967 2 0 l 6 z m w 1 T ltflu M x w .M fi Y z 9 5.5: Z aw INVENT OR m m d \w w J ff W Z Z Z 0. 6 7 m f: ,m M z WM n A Q 7 Y 4r 6 B 7 w 3 0 Z Z L n W I m w; w x L ATTORNEYS United States Patent 3,434,619 FLOATING ROOF SEAL Ardell H. Nelson, Coraopolis, Pa., assignor to Pittsburgh- Des Moines Steel Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Feb. 20, 1967, Ser. No. 617,335 Int. Cl. B65d 87/418 US. Cl. 220-26 19 Claims ABSTRACT OF THE DISCLOSURE A tank having a bottom and a side shell has a floating roof therewithin floating on fluid supported within the tank, and sealing means is provided between the roof and the side shell of the tank. The sealing means includes a plurality of abutting units disposed peripherally about the roof and sealing the annular space between the roof and the shell of the tank. Each of the individual units includes an outer flexible wall portion having opposite ends which are clamped between a pair of longitudinally extending plates to provide a closed space Within the wall portion. This space is filled with a suitable material, and equalizing means is incorporated in each individual unit to provide communication between the interior of the unit and the exterior thereof.

Background 0] the invention The present invention relates to sealing means associated with the floating roof of a fluid storage tank wherein the roof rises and falls with the level of the fluid within the tank, and the sealing means is adapted to provide an eflective seal between the outer surface of the roof and the inner surface of the shell of the tank at all times.

The present invention relates to a floating roof seal of the type incorporating a plurality of individual closed and substantially sealed units which are disposed peripherally about the roof. An arrangement of this type is illustrated in U.S. Patent No. 3,014,613. In this aforementioned patent as in the arrangement of the present invention, a plurality of adjacent units are disposed in abutting relationship with one another, and similar to a first form of the present invention, the units contain liquid therein, interconnections being provided between adjacent units to allow liquid to flow therebetween so as to equalize the hydrostatic pressure in the various individual units.

One of the difiiculties with an arrangement such as shown in the aforementioned US. patent is the fact that a relatively rigid interconnection is provided between the upper portion of the individual units and the roof. With such an arrangement, the amount of variation of the annular space betwee the roof and the shell of the tank is limited, and if the roof should move too far in a lateral direction, the radially outward portion of the sealing means will not maintain a sealing contact with the inner surface of the shell of the tank.

A further difficulty with the structure as shown in the aforementioned US. patent is the fact that the individual units must be assembled in the field since it is necessary to have access to the interior of the adjacent units in order to interconnect the units with one another to provide the equalizing means aforedescribed. This arrangement further makes it excessively difiicult to remove and replace a single unit since access must be gained to the units at either side thereof in order to disconnect the equalizing means when removing a particular unit.

Additionally, the hold-down means of the aforementioned patent structure is completely separate and independent from the equalizing means thereby requiring separate components for accomplishing these purposes.

Summary 0 the invention In the arrangement of the present invention, the various individual units of the sealing means are pivotally interconnected with the roof for swinging movement with respect thereto. This enables the individual sealing units to accommodate a much greater variation in the annular space between the roof and the tank shell and to maintain an effective seal therewith than is possible with the structure as shown in the aforementioned US. patent. Furthermore, the modifications of the invention incorporating material within the sealing units other than liquid are buoyant so that they tend to float upon liquid in the associated storage tank thereby enabling the sealing units to seal a greater annular space than is possible with the structure of the aforementioned patent. Furthermore, where polyurethane foam or fiberglass is employed as the material within the sealing units, this material is pre-compressed so as to enable the sealing units to expand outwardly to fill a relatively large annular space.

The individual sealing units of the present invention need not be assembled in the field, but may be prefabricated since it is not necessary to gain access to adjacent units to interconnect the equalizing means of adjacent units. When it is desired to remove or replace a single unit of the present invention, this may be readily accomplished from above the units without gaining access to ad'- jacent units.

The structure of the present invention further reduces the complexity of the arrangement by providing equalizing means which also forms a portion of the hold-down means. In the modifications of the invention incorporating material other than liquid within the individual units, the equalizing means additionally forms part of the suspension means for the individual units thereby further reducing the number of structural components An object of the present invention is to provide a new and novel floating roof seal which enables an effective seal to be maintained where relatively wide variations occur in the annular space between the roof and the tank shell; and wherein the individual units may be prefabricated and easily removed and replaced when desired; and further wherein the equalizing means also serves as part of the hold-down means; and further wherein in certain modification s of the invention it also serves as part of the suspension means.

Brief description of the drawings FIG. 1 is a vertical section through a storage tank incorporation the floating roof seal of the present invention;

FIG. 2 is a sectional view taken substantially along line 22 of FIG. 1 looking in the direction of the arows;

FIG. 3 is a sectional view taken substantially along line 33 of FIG. 2 looking in the direction of the arrows;

FIG. 4 is a sectional view taken substantially along line 44 of FIG. 2 looking in the direction of the arrows;

FIG. 5 is a view similar to FIG. 2 illustrating a modified form of the invention;

FIG. 6 is a sectional view taken substantially along line 6-6 of FIG. 5 looking in the direction of the arrows;

FIG. 7 is a view similar to FIG. 6 illustrating a further modified form of the invention;

FIG. 8 is a view similar to FIG. 5 illustrating the structure as shown in FIG. 7 of the drawings;

FIG. 9 is a sectional view similar to a portion of the structure shown in FIG. 2 and illustrating a modification of the invention;

FIG. is a sectional view similar to FIG. 9 illustrating a still further modified form of the invention;

FIG. 11 is a view of a still further modified form of the invention partly broken away and partly in section; and

FIG. 12 is a view similar to FIG. 11 illustrating still another modified form of the invention.

Description of the preferred embodiments Referring now to the drawings wherein like reference characters designate corresponding parts throughout the several views, a conventional storage tank is indicated generally by reference numeral 10, the tank including a subsantially cylindrical vertically extending shell or side Wall 12 and having a closed bottom 14. The tank includes an upper open end 16. A floating roof -is indicated generally by reference numeral 18, the floating roof being supported upon a body of fluid disposed within the tank. In a typical example, the fluid may comprise fuel oil or the like.

The roof 18 is includes a generally cylindrical outer side wall having a peripherally extending radially outwardly directed flange 32 at the upper edge thereof. A generally frusto-conical annular upper wall portion 34 is secured at the outer periphery thereof to the inner surface of side wall 30, and a similar bottom wall 36 is in clined in the opposite direction inwardly from the lower portion of side wall 30. The inner porions of upper and lower walls 36 are interconnected by a substantially cylindrical inner wall 38 having a substantially circular plate 40 rigidly interconnected with the inner surface thereof so as to close the central portion of the roof. An annular bumper member 42 is secured to the lower surface of wall 36 of the roof at the outer periphery thereof.

7 A plurality of separate individual and substantially identical sealing units indicated generally by reference numeral are provided peripherally about the outer surface of the roof, adjacent ones of these sealing units being in abutting relationship with one another to provide a substantially continuous seal around the roof within the annual space between the roof and the shell of the tank.

Each of the individual sealing units includes an outer flexible wall portion 52. This wall portion may be formed of any suitable flexible material, and in a typical example may comprise a sheet of material of polyurethane having a further sheet of nylon reinforcement on one surface thereof. In any event, the wall portion is sufiiciently flexible so as to deform into the various configurations required to fill the annular space between the roof and the tank shell, and further to fit about any irregularities which may exist on the outer surface of the roof or the inner surface of the tank shell.

As seen most clearly in FIG. 4, the flexible wall porion 52 may be formed of a sheet of material having opposite closed ends and defining free end edges 54 and 56 which are overlapped with one another. These edges are clamped between a lower elonagted rigid plate 60 and an upper similar elongated plate 62. The

plates

60 and 62 are clamped to one another by a plurality of threaded studs 64 rigidly aflixed to plate 60 and extending through suitable holes provided in the

edge portions

54 and 56 of the flexible wall portion and similar holes provided in the upper plate 62. Nuts 66 are threaded on the upper threaded ends of studs 64 for clamping the flexible wall portion in the position shown so as to provide a substantially closed and sealed inner space within the wall portion.

The suspension means for suspending each of the individual units includes a pair of

suspension members

70 and 72 operatively connected with each unit. The lower ends of each of

members

70 and 72 are rigidly secured as by welding to the upper surface of plate 62. The spacing of the suspension members is an important consideration, and the spacing is such that the distance peripherally around the roof, or longitudinally of the associated plate 62 is substantially one-half the over-all length of the associated sealing unit extending in a similar direction.

Each of

members

70 and 72 is of identical construction, and as seen in FIG. 3, member 72 includes an angularly extending portion 74 which is threaded on the outer end thereof. Portion 74 extends through an enlarged hole 76 provided in the side wall 30 of the roof, and a nut 78 is threaded on the outer threaded end of portion 74.

The arrangement is such that a loose pivotal connection is provided between each of the suspension members and the roof whereby the units attached to the suspension members are adapted to swing with respect to the roof and to thereby readily accommodate the sealing means to wide variations in the annular space between the roof and the tank shell. It will of course be understood that suspension member 70 also has a loose pivotal connection with the side wall 30 in exactly the same manner as suspension member 72 as shown in FIG. 3.

The equalizing means of this form of the invention includes a pair of conduit members 80 and 82 which are open at the opposite ends thereof and which are rigidly secured as by Welding to the undersurface of plate 60 as indicated by reference numerals 84 and 86 respectively. These conduit members extend through suitable holes provided in

plates

60 and 62 as well as in the overlapping edge portions of the outer flexible wall portion.

An elongated rigid member '90 has the opposite ends thereof rigidly affixed to equalizing members 80 and 82.

The lower ends of members 80 and 82 along with the elongated member 90 serves as a hold-down means for the individual sealing unit preventing the lower part of the flexible wall portion of the sealing unit from being drawn excessively in an upward direction upon certain relative movement of the roof with respect to the tank shell.

As seen most clearly in FIG. 2, the upper ends of the adjacent equalizing conduits of adjacent sealing units are interconnected by a conduit portion 94 formed of a suitable fiexible material such as rubber or the like. The opposite ends of conduit portion 94 are clamped upon the upper ends of equalizing conduits 80 and 8-2 by clamp means 96 and 98 respectively such as a conventional hose clamp or the like. It is apparent that interconnecting means 94 provides a flow path between the equalizing means of adjacent sealing units, and that the interconnecting means may be readily removed and replaced when required.

Referring now to FIGS. 5 and 6 of the drawings, a modified form of the invention is illustrated. This form of the invention is in many respects identical with that previously described, and similar parts have been given similar reference numerals primed. The roof is of the same construction as that previously described, the only difference being that the holes 76' formed in the side wall 30 of the roof may be of slightly larger size to accommodate the combined equalizing means and suspension means as hereinafter described.

The outer flexible wall portion 52' is of substantially the same construction as that previously described and has opposite edge portions which are clamped between two plates 60' and 62 in the very same manner as previously discussed by the intermediary of studs 64' and nuts 66' as will be readily apparent.

In this form of the invention, the

suspension members

70 and 72 of the modification illustrated in FIGS. l-4 have been eliminated.

The equalizing means in this form of the invention includes two rigid conduit members and 112 which are hollow and open at the opposite ends thereof, these conduit members being rigidly secured as by welding to the undersurface of plate 60' and extending through aligned holes provided in plate 62 as well as the edge portions of the associated flexible wall portion. Lower portions of

conduit members

110 and 112 support opposite ends of a rigid elongated member 114 extending therebetween whereby the lower portions of

conduit members

110 and 112 and the associated member 114 cooperate to form a hold-down means for the outer flexible wall portion.

As seen most clearly in FIG. 6, the upper end of member 110 terminates in an angularly offset portion 120 which extends through the hole 76' provided in the side wall of the roof. This end portion 120 is provided with external threads thereon which receive a nut 122 for retaining member 112 in position.

It will be noted that the arrangement is such as to provide a loose pivotal interconnection between member 112 and the roof. It should be understood that member 110 is interconnected with the roof in exactly the same manner as member 112 as illustrated in FIG. 6.

It will be noted with the arrangement as above described that the equalizing

conduit members

110 and 112 also form a portion of the suspension means for providing a pivotal interconnection between the roof and the associated sealing unit to permit swinging movement of the sealing unit with respect to the roof.

In this form of the invention, the material disposed within the closed space in the outer flexible wall portion may comprise a resilient plastic material such as polyurethane foam or fiberglass and the like. As seen most clearly in FIG. 6, the material within the sealing unit may be in the form of a plurality of layers or strips of material 126 disposed in abutting relationship with one another so as to substantially fill the space within the outer wall portion 52'.

The material placed within the outer Wall portion in this form of the invention is initially assembled so as to be pre-compressed Within the outer wall portion so that when the sealing unit is disposed in operative position, the pre-compressed material therewithin will tend to make it expand at all times into engagement with the roof and the tank shell.

The equalizing means in the form of the

hollow conduits

110 and 112 allows air to enter into the sealing unit as it expands or to be exhausted therefrom as it contracts under pressure, thereby permitting the sealing unit to readily adapt itself to the size of the space between the roof and the tank shell.

Additionally, the material employed in this form of the invention is of a buoyant nature so that when resting upon a liquid within the tank, it will tend to be buoyed in an upward direction thereby tending to cause the sealing unit to completely fill the space between the roof and tank at all times.

It should be noted that in this form of the invention,

members

110 and 112 actually comprise portions of not only the equalizing means, but the suspension means and the hold-down means as Well thereby eliminating the necessity of providing separate components for serving these different functions.

Referring now to FIGS. 7 and 8 of the drawings, a still further modified form of the invention is illustrated. Here again, the roof construction as well as the constructions of the outer flexible wall portion and the means for clamping the edge portions thereof to one another are substantially identical with that shown in FIGS. 1-4 inclusive and have been given the same reference numerals primed.

The members 110' and 112 are identical with

members

110 and 112 as described in connection with FIGS. 5 and 6 and serve the same purpose as in this form of the invention.

The only difference between this form of the invention and that shown in FIGS. 5 and 6 is the arrangement of the material within the outer flexible wall portion. In the modification illustrated in FIGS. 7 and 8, an inner layer of material is suitably secured as by bonding to the inner surface of the outer wall portion 52, and an outer layer of material 132 is similarly secured to the outer wall portion opposite to the layer 130. Each of layers of material 130 and 132 are formed of a suitable resilient deformable material such as fiberglass or the like.

Relatively rigid

metallic plate members

134 and 136 are secured to the inner surfaces of layers 130 and 132, the upper and lower edges of these plates as seen in FIG. 7 being curved inwardly to permit the layers of material adajcent thereto to conform to the shape of the plates upon movement of the sealing means into different operative positions.

Plates

134 and 136 are constantly urged away from one another by a plurality of compression springs 140 having the opposite ends thereof disposed within suitable cuplike retaining means 142 mounted on the inner surfaces of

plates

134 and 136. It is apparent that these compression springs will normally urge the opposite portions of the sealing means into engagement with the roof and the tank shell at all times. The sealing means is of course adapted to swing with respect to the roof as in the previous modications.

The spacing of the combined equalizing and suspension members in the forms of the invention shown in FIGS. 5- 8 inclusive should be approximately the same as that of the spacing of the

suspension members

70 and 72 of the modication shown in FIGS. 14 or in other words, the spacing of member 110 from member 112 and 110' from 112. should be approximately one-half the longitudinal dimension of the associated sealing unit.

Referring now to FIG. 9, a further modified form of the invention is illustrated. This form of the invention is substantially identical with that shown in FIG. 2, and similar parts have been given the same reference numerals primed. The structure is identical with that shown in FIG. 2 except for equalizing conduits which has been substituted for equalizing conduit 80 of the modification previously described. Conduit 150 is secured as by welding indicated at 152 to the undersurface of plate 60', and the lower end 154 of conduit 150 is open as is the lower end of equalizing conduit 80 shown in FIG. 2.

Equalizing conduit 150 is additionally provided with a hole 156 formed therein just beneath plate 60. In this form of the invention, hole 156 is provided in the equalizing conduit as close to the undersurface of plate 60 as possible. With such an arrangement, if any gas should be trapped in the upper portion of the space within the sealing unit, the gas can readily escape through hole 156 to thereby improve the performance of the over-all sealing means.

Referring now to FIG. 10, this form of the invention is also quite similar to that shown in FIG. 2 and the same parts have been given similar reference numerals primed. In this form of the invention, an equalizing conduit 160 has been substituted for the equalizing conduit 80 shown in FIG. 2.

Equalizing conduit 160 is secured as by Welding indicated at 162 to the undersurface of plate 69. A hole 164 is provided in conduit 160 as close as possible to the undersurface of plate 60' and is adapted to enable liquid or gas in the sealing unit to flow through the conduit to an adjacent sealing unit. The lower end of conduit 160 is closed by a wall portion 166.

It should be understood that each of the equalizing conduits of the various sealing units may be of a construction shown in either FIG. 9 or FIG. 10 if so desired.

Referring now to FIG. 11, still another modified form of the invention is illustrated. This modification is similar to that shown in FIG. 2 in that the sealing unit is filled with a liquid. Parts similar to that shown in FIG. 2 are provided with the same reference numerals primed. The essential difference between this form of the invention and that shown in FIG. 2 is that instead of having a pair of equalizing conduits extending into the sealing means at spaced portions thereof, a single centrally located equalizing conduit 170 is provided. This equalizing conduit is secured as by welding indicated by reference numeral 172 to the undersurface of plate 60'. The lower end of conduit 170 is open, and a pair of holes 176 are provided in the conduit at a point spaced as nearly as possible to the undersurface of plate 60. Here again, these holes 176 are provided for the purpose of allowing any gas which may be trapped in the upper portion of the sealing means to readily escape therefrom.

The hold-down means in this form of the invention comprises a pair of

rigid members

178 and 180 rigidly secured to conduit 170 and extending in opposite directions therefrom.

The upper end of conduit 170 extends outwardly of the sealing means in the same manner as described in connection with equalizing conduit 80, equalizing conduit 170 terminating in a T-portion 184. A flexible conduit 186 is connected with one side of the T-portion, and a further flexible conduit 188 is secured to the other side of the T- portion.

Conventional clamping members

190 and 192 are provided for holding the flexible conduits in place on the T-portion. These flexible conduits will of course connect adjacent sealing units with one another.

Referring now to FIG. 12, still another form of the invention is illustrated. Here again, parts similar to those shown in FIG. 2 have been given the same reference numerals primed. A single central equalizing conduit 200 is provided which is secured as by welding indicated by reference numeral 202 to the undersurface of plate 60. A pair of holes 204 are provided in conduit 200 as near as possible to the undersurface of plate 60'. The difference between this modification and that shown in FIG. ll is that the lower end of conduit 200 is closed by a wail portion 206. The hold-down means includes a pair of

rigid portions

208 and 210 secured to conduit 200 and extending in diametrically opposite directions therefrom.

Conduit 200 extends outwardly of the sealing means and terminates in a T-portion 214. A first flexible conduit 216 is connected with one side of the T-portion and a second flexible conduit 218 is connected with the opposite side of the T-portion. The flexible conduits are secured to the T-portion by

conventional clamps

220 and 222. This form of the invention is substantially identical with that shown in FIG. ll with the exception that all of the material within the closed space defined by the sealing means will pass through the holes 204 since the lower end of the conduit 200 is closed.

It should be understood that in the modification shown in FIGS. 9-12, the various equalizing conduits may be provided with one or more holes disposed therein remote from the lower end thereof, and such lower end may be either open or closed as desired. The holes are preferably formed in an upper portion of the conduits adjacent to the plate from which they are supported so that gas trapped in the upper portion of the sealing means can readily escape therefrom.

It is apparent from the foregoing that there is provided according to the present invention a new and novel floating roof seal which is pivotally interconnected with the roof so as to enable eflective sealing with wide variations in the size of the annular space between the roof and the tank shell. The buoyancy of the forms of the invention illustrated in FIGS. *8 also assist in maintaining the desired effective seal. The individual sealing units may be prefabricated and simply mounted in place at the job site. In the form of the invention illustrated in FIGS. 14, the connection between the equalizing means of adjacent units is readily accessible from the top of the units, and it is a simple matter to remove and replace a single unit when desired. Additionally, the arrangement of the various modifications are such that the equalizing means and the hold-down means include common components. Furthermore, in the modifications shown in FIGS. 5-8, the equalizing means additionally forms a portion of the suspension means tnereby further reducing the number of components required.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive.

I claim:

1. In combination with a fluid storage tank having a bottom and a side shell, a floating roof disposed within the tank to rise and fall with the level of the fluid within the tank, said roof providing an annular space therearound between the same and said side shell, sealing means supported by said roof and disposed in said annular space for engaging the outer surface of said roof and the inner surface of said shell, said sealing means comprising a plurality of separate units disposed peripherally about said roof and adjacent to one another, each of said units including an outer flexible wall portion defining a substantially closed space therewithin, material disposed within said space defined by the wall portion and adapted to maintain said outer flexible wall portion in engagement with said roof and said shell at all times, equalizing means providing communication between said space within each of said outer flexible wall portions and the exterior thereof to permit expansion and contraction of the individual units, said equalizing means comprising conduit means having one end thereof extending outwardly of the associated unit, the opposite end of said conduit means extending downwardly into the associated unit a major portion of the vertical height of said unit and cooperating with a member supported thereby to form a hold-down means for the flexible wall portion of the associated unit, and suspension means for suspending each of said sealing units from said roof, the suspension means operatively associated with each of said units defining a movable interconnection between each of said units and the roof to permit movement of each of the over-all units relative to the roof.

2. Apparatus as defined in claim 1 wherein the suspension means operatively associated with each of said units includes a pair of suspension members, the associated unit having a certain length, said suspension members being spaced peripherally about the roof a distance which is substantially one-half the length of the associated unit.

3. Apparatus as defined in claim 1 wherein the material disposed within the space of each of said units is liquid, the associated unit defining a substantially sealed wall portion so that the liquid is maintained within the associated unit and can only escape therefrom through said equalizing means.

4. Apparatus as defined in claim 1 wherein the material within each of said units comprises a resilient deformable plastic substance which is precompressed when initially installed within the units so as to enable the units to conform to the size of the space between the roof and the shell of the tank.

5. Apparatus as defined in claim 1 wherein said material within the space of each of said units includes a layer of resilient deformable material at the inner and outer sides of each of said units, and spring means disposed between said layers and urging said layers away from one another so as to maintain the desired degree of contact of each of said units with the roof and the tank shell.

6. Apparatus as defined in claim 1 wherein said equalizing conduit means has means thereon providing a loose pivotal interconnection with said roof so that the conduit means forms part of the suspension means for suspending the associated unit for swinging movement with respect to the roof.

7. Apparatus as defined in claim 1 wherein said equalizing means includes a pair of conduit means extending within each of said units, said supported member being secured to and supported by said pair of conduit means in each of the units.

8. Apparatus as defined in claim 1 wherein the suspension means operatively associated with each unit has a loose pivotal interconnection with the roof to permit swinging movement of the associated unit with respect to the roof and to allow relative radial movement of the suspension means with respect to the roof at the point of interconnection therewith.

9. Apparatus as defined in claim 8 wherein each of said outer flexible wall portions of each unit has opposite edge portions, means for clamping the opposite edge portions with respect to one another to provide a substantially sealed unit, said clamping means being disposed at the upper portion of each of said units.

10. Apparatus as defined in claim 8 wherein each of said units has opposite closed end portions, the end portions of adjacent units being disposed in abutting relationship with one another to provide a continuous seal around the roof.

11. Apparatus as defined in claim 1 including means interconnecting the outwardly extending portions of the conduit means of adjacent units so as to provide a flow path between adjacent units.

12. Apparatus as defined in claim 11 wherein said interconnecting means is removably attached to the associated conduit means so as to be readily removable when required, said interconnecting means being disposed above the upper portion of each of said units so as to be readily accessible from above the units.

13. Apparatus as defined in claim 11 wherein said suspension means includes a separate member spaced from said equalizing means, said member being fixedly secured at the lower end thereof to an upper portion of the associated unit, the upper end of said member having a loose pivotal interconnection with the roof to permit swinging movement of the associated unit with respect to the roof and to allow relative radial movement of the suspension means with respect to the roof at the point of interconnection therewith.

14. Apparatus as defined in claim 1 wherein said equalizing means includes conduit means extending into the space in each of said units the opposite end of each of said conduit means extending outwardly of an associated unit, means interconnecting the outwardly extending portions of the conduit means of adjacent units so as to provide a flow path between adjacent units, at least one of said conduit means having a hole tormed therein at the upper portion of the space defined by the associated sealing unit to enable gas to readily escape from the associated unit.

15. Apparatus as defined in claim 14 wherein the lower end of said conduit means having said hole formed therein is open.

16. Apparatus as defined in claim 14 wherein the lower end of said conduit means having said. hole formed therein is closed.

- 17. Apparatus as defined in claim 14 wherein said conduit means having the hole formed therein is the only conduit means extending into the associated sealing unit and is disposed centrally thereof.

18. Apparatus as defined in claim 17 wherein the lower end of the conduit means having said hole formed therein is open.

19. Apparatus as defined in claim 17 wherein the lower end of the conduit means having said hole formed therein is closed.

References Cited UNITED STATES PATENTS 1,913,643 6/1933 Smith.

2,085,752 7/1937 Horton et al.

2,914,212 11/1959 Fino.

3,014,613 12/1961 Anderson.

3,055,533 9/1962 Reese et al.

3,154,213 10/1964 Ulm.

FOREIGN PATENTS 730,368 5/1932 France.

JOSEPH R. LECLAIR, Primary Examiner. JAMES R. GARRETT, Assistant Examiner.