Leaktight covering fixed to a framework

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Patent issued

01/12/1993

Inventor(s):	Ovaert, Francis Desgouilles, Henri
Assignee	Axter (Saint-Quentin en Yvelines)
Application	No. 07/654,672 filed on 02/14/1991
Current US Class	52/410, 52/512, 411/383
Field of search	52/408, 52/410, 52/512, 52/409, 52/412, 411/389, 411/383, 411/546, 411/338, 411/339
International Classes:	E04B 706
Examiners
Primary	Scherbel David A.
Secondary	Nguyen Kien
Attorney, agent or firm:	Wenderoth, Lind & Ponack
US patent references	4453361, 4604846, 4651490, 4736561, 4787775, 4932819, 4934887, 5018329, 5033242
Foreign patents	90 01755 (02/14/1990, FR), 2803709 (07/31/1979, DE), 2838566 (02/29/1980, DE), 3040794 (04/30/1981, DE), 3515734 (10/31/1986, DE), 2553836 (03/31/1985, FR), 2111115 (05/31/1983, GB), 2122234 (12/31/1983, GB)

A leaktight covering, in particular for an industrial building, includes aloadbearing element adapted to be fixed to a framework element of thebuilding, a layer of an insulating material arranged on the loadbearingelement, and a cladding covering the layer of insulating material, withconnection structure holding such three components assembled together. Afirst member is used, on the one hand, to ensure fixing of the loadbearingelement to the framework element and, on the other hand, forms part of theconnection structure. A second member is linked to the first member and tothe cladding. In a first embodiment, the first member is a screw screwedinto the framework element, and the connection structure includes ahollow, cylindrical intermediate piece, a bottom of which is fixed to theloadbearing element via the screw.
BACKGROUND OF THE INVENTION
The present invention relates to insulating and leaktight coverings, and inparticular coverings for industrial buildings.
These coverings fixed to a framework comprise a thermal insulation betweena loadbearing element and a cladding. This insulation is principallyrealized by plates or panels laid touching one another. These plates arefastened firmly to the loadbearing element by a mechanical fixing meanswhen a support consists of profiled steel sheets.
The mechanical fixing means consists of a screw, or a rivet or a boltfastened firmly to the profiled steel sheet by drilling or by welding. Atits upper part, a head of the screw, rivet or bolt has a washer of smalldimensions, of a diameter of the order of 50 to 70 mm.
The cladding is fastened firmly to the insulating plates by adhesivebonding or by welding using a heat source, usually with a flame or airtorch, over the entire surface of the insulating panels and/or at thelevel of the washers of the mechanical fixing means. The latter can beimproved for welding by an appropriate surface coating or by a washer madefrom the same material as the cladding, and of larger dimensions, placedin between the metal washer and the underlying insulating panel.
A more recent technique provides for a first bed of foils constituting thelower part of the cladding to be unwound dry over the insulating panels.The mechanical fixing means then traverse the foil bed and the insulatingpanels. In the case of panels sensitive to the flame of a torch, a priorheat screen can be employed on the insulator. The upper part of thecladding is then adhesively bonded or welded to the lower part comprisingits visible washers.
Another technique provides mechanical fixing means at the level of lapjoints of the widths of the cladding. A lapped part is adhesively bondedor welded, on the one hand, to the edge of the adjacent width and, on theother hand, to the small washers of the fixing means.
The wind creates considerable localized compression and suction forces onthe covering (vortices, shielding effect behind a wall or a salient partof the roofing). The forces are exerted on the outer surface and hence onthe cladding, which ultimately stresses the loadbearing element and thestructure of the building.
In the area lying between the cladding and the loadbearing element, theseforces create, at the level of one or more fixing means, tear-away forcesperpendicular and parallel to the covering surface. These latter forcesare more substantial the greater the spacing between the fixing devices.They can result in the cladding ripping at the head of the fixing meansand/or the fixing means being torn away at the level of their connectionto the framework or the loadbearing element under a torque or tractioneffect.
For these two latter techniques, at least one sheet of the cladding ispierced by the mechanical fixing means.
In all cases, in order to resist the suction forces created by the wind,the French standards defined within the D.T.U. 43.3 and common practiceprovide for a minimum of five fixing means per m.sup.2 of roofing, basedon the fact that a fixing means resists a tear-away force of approximately900N.
A rupture occurs at the level of the plane of the adhesive bonding of thecladding to the washer, or as a result of the head of the fixing meansbecoming dislodged and passing through the washer, or as a result of thefixing means being torn away through the profiled steel sheet. The valuesof the rupture are relatively homogeneous, of the order of 900 to 1300N.
The large number of fixing means makes implementation lengthy andexpensive. Furthermore, the performance of the cladding is considerablydiminished at the level of the fixing means because the cladding ispartially pierced, or because it can be punched by the head of the fixingmeans passing through the washer, or alternatively torn at the peripheryof the washer when the latter is locked, redundantly, on the rod of the,fixing means, as described in French Patent 1,522,378. Such phenomenonfavors the breaking of the weld between the bolt and the profiled steelsheet. These disadvantages are considerably amplified when the insulatingpanels are compressible but elastic.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a covering which issimpler and quicker to implement than the conventional openings coveringand, moreover, which has an improved resistance to wind.
To this end, the invention provides a leaktight covering, in particular foran industrial building, comprising a loadbearing element adapted to befixed to a framework element of the building, a layer of an insulatingmaterial arranged on the loadbearing element, and a cladding covering thelayer of insulating material, connection means being provided in order tomaintain such three components assembled together. The connection meanscomprise a first fixing member fixing the loadbearing element to theframework and comprising, above the loadbearing element, an extensionpiece of a length substantially equal to the thickness of the insulatinglayer and a flexible plate and a second fixing member bearing on suchflexible plate via a widened head and/or a rigid washer and fixed to theextension piece. The dimension of the widened head or of the rigid washeris between the maximum dimension of the first or the second member in thevicinity of the outer surface of the layer of insulating material and thedimension of the flexible plate. The cladding is fixed only to theflexible plates.
In this manner, the cladding which will be fixed to a number of flexibleplates will be fastened firmly to the framework moreover, the inventionalso makes it possible to fasten the loadbearing element firmly to theframework in such a way that all the suction forces to which the coveringis subjected will be transmitted to the framework element, purlin or beam.
This high-performance device permits the use of at most one fixing meansper m.sup.2 of covering (or even one per 2 m.sup.2), thus dividing thetotal number of fixing means by more than five as compared with theconventional techniques described above.
In the case of a steel framework, the above-mentioned screw can be aself-tapping screw. In the case of a concrete framework, theabovementioned screw is engaged in a metal insert of the framework element.

We claim:
1. A leaklight covering, particularly for an industrial building,comprising:
a metal sheet loadbearing element adapted to be fixed to a frameworkelement of the building;
a layer of insulating material arranged on and above said loadbearingelement;
a watertight cladding covering said layer of insulating material;
a plurality of connection means for maintaining said loadbearing element,said layer of insulating material and said cladding assembled together,each said connection means comprising:
a first fixing member for fixing said loadbearing element to the frameworkelement, said first fixing member including, above said loadbearingelement, an elongated extension piece extending upwardly substantially toan upper surface of said layer of insulating material;
a flexible plate positioned on said upper surface of said layer ofinsulating material;
a second fixing member fixed to said extension piece and having a rigiddistribution element bearing on said flexible plate; and
said rigid distribution element having a dimension in a directionperpendicular to said extension piece between a maximum dimension in saiddirection of said first or second fixing member in the vicinity of saidupper surface of said layer of insulating material and a dimension in saiddirection of said flexible plate;
said flexible plates of said plurality of connection means being spacedfrom one another; and
said cladding being bonded only to said flexible plates and to saiddistribution elements of said plurality of connection means.
2. A covering according to claim 1, wherein said rigid distribution elementcomprises a widened head of said second fixing member.
3. A covering according to claim 2, wherein said flexible plate is fastenedfirmly to said rigid distribution element.
4. A covering according to claim 1, wherein said rigid distribution elementcomprises a rigid washer.
5. A covering according to claim 1, wherein said first member furtherincludes a screw to be screwed into the framework element, and saidelongated extension piece comprises a hollow, cylindrical intermediatepiece having a bottom which is fixed to said loadbearing element by saidscrew.
6. A covering according to claim 1. wherein said first member furtherincludes a screw having a shaft to be screwed into the framework elementand having a head, and said elongated extension piece comprises a rodextending upwardly from said head opposite said shaft of said screw.
7. A covering according to claim 1, wherein said elongated extension piecehas an axis which is offset relative to an axis of fixing of saidloadbearing element to the framework element.
8. A covering according to claim 1, wherein, if a designates a diameter ofsaid rigid distribution element, d a diameter of said first fixing memberor of said second fixing member in said vicinity of said upper surface ofsaid layer of insulating material, D a diameter of said flexible plate,and Rt a mechanical strength under tension of said flexible plate, thefollowing conditions exist:
Rt.pi.a.gtoreq.5000N
a-d.gtoreq.70 mm
D-a.gtoreq.100 mm
9. A covering according to claim 1, wherein said flexible plate has a tearstrength Rd greater than or equal to 200N, and a diameter d of said firstfixing member or of said second fixing member in said vicinity of saidupper surface of said layer of insulating material is at least equal to 6mm.
10. A covering according to claim 1, wherein fixing of said second fixingmember to said first fixing member is effected by means selected from thegroup comprising screwing, clip-fastening or bayonet fixing means.
11. A covering according to claim 1, wherein said layer of insulatingmaterial consists of mineral wool having a density less than 120kg/m.sup.3 or of glass wool having a density less than 90 kg/m.sup.3.

BRIEF DESCRIPTION OF THE INVENTION
Other features and advantages of the invention will become apparent fromthe description which follows of illustrative embodiments of theinvention, made with reference to the attached drawings, in which:
FIG. 1 is a diagrammatic sectional representation of a first embodiment ofthe invention;
FIG. 2 is a diagrammatic sectional representation of a second embodiment ofthe invention;
FIG. 3 is a view in section along a framework element and corresponds tothe embodiment in FIG. 2; and
FIGS. 4 and 5 are sectional views illustrating a particular embodiment ofthe invention.
DETAILED DESCRIPTION OF THE INVENTION
A framework element can be seen in FIGS. 1 and 2 would consists of a steeljoist 1 constituting a purlin of a framework. A loadbearing element 2consisting of a profiled steel sheet is arranged transversely on purlins1.
An insulating layer 3 consisting, for example, of plates of insulatingmaterial is placed on the load-bearing element 2. The covering or roofingis completed by a cladding 10 which is placed on the outer face of theinsulating layer 3.
A fixing device according to the invention comprises a first fixed membercomprising a screw 4 which is fixed to the purlin 1 with interposition ofthe support element 2 which is therefore in this way firmly fastened tothe framework.
This first member serves firstly to fix the loadbearing element 2 to theframework purlin 1, and also constitutes an element forming part of aconnection means for the three components of the covering, namely theloadbearing element 2, the insulating layer 3 and the cladding 10.
The screw 4 is advantageously a self-tapping screw. In the case of aconcrete framework, screw 4 engages in a metal insert of the frameworkelement.
A head 5 of the screw 4 has an extension piece aligned with the shaft ofthe screw and arranged on the opposite side of the head 5. In the firstembodiment of FIG. 1, this extension piece consists of an internallythreaded, hollow, cylindrical intermediate piece 6 which is open at itsfree end and a bottom 20 of which is fixed to the loadbearing element viathe screw 4. In the embodiment in FIG. 2, the extension piece consists ofa threaded rod 7. The length of the cylinder 6 or of the rod 7 issubstantially equal to the sum of the thicknesses of the insulating layer3 and of the loadbearing element 2.
A second member comprising a part including a rigid washer is fastenedfirmly to the abovementioned first member. In the case of FIG. 1, thissecond member is a screw 8 which engages in the cylinder 6, which has amilled flat head and on which is engaged a rigid washer 9 of diameter andforming a rigid distribution element.
In the embodiment in FIG. 2, the second member consists of a sort of plug11 which has an internally threaded tubular part 12 which interacts withthe rod 7 and which is surmounted by a rigid flat head 13 constituting abearing washer or rigid distribution element similar to the rigid washer9.
Lastly, the fixing device comprises a flexible plate 21 which is placedbetween the rigid washer 9 or the rigid flat head 13 and the insulatingpanels 3. Plate 21 is preferably circular, of diameter D and of largedimensions.
Flexible plate 21 is, for example, made from a metal of small thickness andcan comprise a surface coating compatible with the material constitutingthe cladding. It is also possible to use a material comprising areinforcement which is woven or nonwoven, made from glass, polyester,organic material or from a mixture of these components, in which case theplate is coated with a material identical to or compatible with that ofthe cladding.
The abovementioned plate 21 can advantageously be fastened beforehandfirmly to the washer 9 or to the rigid head 13 by adhesive bonding orwelding.
In the embodiment in FIG. 1 comprising a first member consisting of ascrew, it is also possible to provide for the flexible plate to be crimpedbetween two rigid washers corresponding to the washer 9.
The rigid washer 9 or the flat head 13 can have a diameter a of the orderof 80 mm.
The flexible plate 21 must have a mechanical strength under tension whichconforms with the equation R.sub.t .pi.a>5000N and preferably of the orderof 8000N, the mechanical strength under tension R.sub.t being expressed inNewtons per cm width and measured in accordance with the standard NFG07--001. Plate 21 must also have a tear strength Rd (measured inaccordance with the UEATC method 5.4.1., July 1982) which is at leastequal to 200N and preferably of the order of 400N. To this end, thediameter d of the cylindrical piece 6 in the embodiment in FIG. 1, or ofthe second member 11 in the embodiment in FIG. 2, in the vicinity of theouter surface of the layer 3 of insulating material, must be not less than6 mm and preferably of the order of 10 mm.
Moreover, the difference between the diameter D of the plate 21 and thediameter a of the rigid washer 9 or of the flat head 13 must be at leastequal to 100 mm and preferably of the order of 170 mm. As a result, it ispossible to use, for example, a flexible plate whose diameter D is of theorder of 250 mm.
The diameter of the washer or rigid head a and the diameter d of the fixingelement are advantageously selected in such a way that the difference(a-d) is approximately equal to 90 mm and in any case greater than 70 mm.This makes it possible to prevent the flexible plate 21 from allowing therigid piece 9 or 13 to "escape" by slipping, tearing or becomingdislodged.
FIG. 3 is a view in section perpendicular to FIG. 2 and shows the method offixing the loadbearing element 2 to the purlin 1. It can be seen that therod 7 is integrally connected to the head of the self-tapping screw 4which is fixed in a recess of the profiled sheet 2 on the purlin 1 withthe interposition of a washer 14.
The fixing device according to the invention advantageously comprises atleast one thermally insulating element in order to prevent the formationof thermal bridges.
FIGS. 4 and 5 show an alternative embodiment of the invention. This isintended in particular for edge purlins 41 which are directly adjacent toan acroterium or ornamental summit 42.
In this case, the axis of the fixing point of the cladding is offsetrelative to the axis of fixing of the loadbearing element to the purlin.To this end, the first member consists of two screws 51 and 52 arrangedsymmetrically relative to the axis of a purlin 41 which constitutes theaxis of fixing of a profiled sheet 44 to the purlin 41.
Screws 51, 52 serve to fix one end of a base 43 to the purlin 41. Base 43preferably has, in cross-section (FIG. 5), the shape of a U and carries,at one of its ends, a hollow cylindrical member 45 similar to thecylindrical piece 6 in FIG. 1.
It can be seen that the axis of the hollow member 45 is offset relative tothe axis of the purlin 41. It is, of course, possible to provide a similararrangement in which the base 43 supports a rod similar to the rod 7 inFIG. 2.
A covering in accordance with the present invention can be realized asfollows. Firstly, the loadbearing element 2, 44 (profiled sheet) is fixedto the beams or purlins 1, 41 of the framework by means of the fixedmembers 4 or 51, 52. The panels of the insulating layer 3, 46 arepositioned by "impaling" them on the extension pieces 6 and 7 respectivelyof the first members. The flexible plates are positioned where they arenot firmly fastened to the rigid washers, and then the fixing of thesecond members 8, 11 to the first members is carried out so as to fastenthe second members firmly to the loadbearing element and the purlin orbeam. Then the cladding is positioned and is fixed by welding or adhesivebonding to the flexible plate and the rigid washer of the devicesaccording to the invention.
The various mechanical elements (self-tapping screw, first member, secondmember) are dimensioned so as to have a tear strength of the order of5000N. In this way a homogeneous assembly is obtained which has a tearstrength of 5000N, and all of the forces resulting from a suction exertedon the cladding are transmitted directly to the framework by the fixingmembers.
Since the number of fixing means per m.sup.2 is very considerably reduced,the cost and the time taken to install a covering are considerablyreduced, which makes it possible to construct coverings with large surfaceareas, in particular coverings for industrial buildings.
Furthermore, in the event of people moving about on the covering or ofcompressive loads, the cladding follows the movements of the flexibleplate and cannot therefore be torn at the level of the periphery of therigid washer. Highly compressible insulators can be used for theinsulating layer, which makes it possible to reduce further the cost andthis is particularly so in the case where the flexible plate is crimpedbetween two rigid washers.
It is possible, for example, to use mineral wool having a density of lessthan 120 kg/m.sup.3 and preferably equal to 100 kg/m.sup.3 instead ofmineral wool of a density of 150 kg/m.sup.3 which is currently used.
It is also possible to use glass wool with a density of less than 90kg/m.sup.3 instead and in place of a glass wool of a density of 110kg/m.sup.3.