Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVEN~ION
This invention relates to roofing elements and more
particularly but not exclusively to roofing elements having
a great span length for the construction of roofs for
factory buildings and the like.
U,S, Patent Specification No. 1,075,845 (Mllls) discloses
a structural material made up of two parallel spaced wooden
members united by upper and lower skins of sheet metal.
lhis material, if usea for roofing, is subjected to compression
stresses which have to be taken up almost completely by the
wooden members, since the sheet metal upper skin would be
easily overstressed otherwise. Accordingly, the wooden
members must be of ample cross dimensions, entailin~ a great
expenditure of wood. ~urther, the massive wood components
will form heat-conducting bridges between the inside and
outside.
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German Patent Specification No. 812,834 discloses a
hollow all-wood construction element having both outer
skins of wood-based board material and the distance members
formed by composite beams having flanges of wood and webs
of board material, ~eing an all-wood structure this element
lacks fireproofing, contrary to that one afforded by a
sheet metal skin. This structure will àlso involve a weight
penalty due to the provision of two relatively thick outer
skins.
Swedish Patent Specification No. 385,603 provides a
construction element having an upper skin of plywood or
the like and bottom members of channel-shaped sheet metal
profiles bonded to the upper skin. The metal profiles will
form extensive heat-conductive bridging and do only extend
opposite parts of the upper plywood skin whereby fire-proof-
ing becomes ineffectual~ .
SUMMARY OF THE INVE~TION
It is an object of the invention to provide a roofing
element of light-weight construction capable of taking up
great loads over important span lengths,
A further object is to provide a roofing element using
non-metallic material to withstand compression stresses
and sheet metal for taking up tension stresses and for
fire-proofing.
A still further object is to provide a roofing element
wherein heat-conducting bridges are virtually eliminated,
To attain these and f.urther objects the invention provides
a roofing element having a relatively thicker upper skin for
taking up compression stresses, a relatively thinner lower
sheet metal skin for taking up tension stresses and spacing
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members bonded to both skins and extending in the lengthwise
direction of said element, said spacing members being composite
beams of non-metallic or substantially non-metallic material
comprising flange portions and interconnecting, relatively
thin webs.
~ RI~F DESCRIPTION 0~ TH~ ~RAWI~GS
In the drawings
~ig, 1 is a partial perspective view of a roofing element
according to the invention;
~ig. 2 is a top plan view of a stiffening intermediate wall;
~ig. 3 is a cross section view of a joint between two roofing
elements;
Fig. 4 illustrates an alternative mode of joining two elements;
~ig. 5 is a partial perspective view of a second embodiment;
Fig. 6 is a cross section view of a joint between two elements
similar to that one in Fig, 5.
D~SCRIPTIO~ OF TME PR~FERR~D EM~ODIM~TS
The roofing element illustrated in Fig, 1 comprises two
spaced outer skins 1 and 2, an upper skin or sheet 1 of
plywood or the like having a thickness between 6 and 25
millimeters and preferably of the order of 15 millimeters
and a lower sheet metal skin 2, The lower or bottom skin 2
will not be subject to compression stresses when forming
part of a roof and thus can be a thin gauge steel or metal
plate, in the order of 0.4 to 1,0 millimeters. The overall
length of the roofing element may be as great as 12 meters.
~ etween the skins 1 and 2 there are interposed spacing
and force transmitting composite beams 3 which extend
lengthwise of the element and are bonded by their flange
or rim wooden portions 5 to the skins, The bonding agent
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may be a glue or adhesive cement alone or in combination with
nails. ~he beams 3 have an I-shaped profile and have web
portions 4 of a fibrous wood-based material and flanges 5
of wood. The webs 4 have tapered edge portions which engage
corresponding grooves in the flanges and are secured therein -
by a bonding agent so as to form a rigid unit therewith.
In the embodiment shown, three I beams 3 are provided, one
at each lateral side of the element and one along the middle.
For increasing lateral stiffness board sheets 6 having
recessed corners 7 for accomodating the beam flanges may
be fitted inside the elements. ~ike the thin webs 4 of the
beams 3 they have a very low thermal conductivity, whereby,
contrary to metal profiles or metal framework, they do not
provide heat-conducting paths right through the elements.
The regular-shaped spaces defined between the skins 1 and
2 and beams 3 and sheets 6, when provided, are filled by
insulating mats 8 of mineral wool or the like (Fig. 3). As
can be seen, the insulating material need only be recessed
at the lateral edges, corresponding to the size and shape
of the flanges 5. ~he shaping of the insulation as well as
the fitting thereof is easily carried out, therefore.
Alternatively, the insulation may be rigid and bonded to
the surrounding material J thereby increasing stiffness, Such
insulation may be a foamed uretane plastic injected into the
spaces. ~his compound can also be used in the lateral joints
between elements (Fig. 3), to form a body 9 keying two
elements lateral~y together by filling out the space between
the webs and flanges of two parallel beams belonging to two
juxtaposed elements.
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In Fig. 4 there is illustrated another embodiment of the
lateral joint between two roofing elements. In this structure
the interspace between the webs 4 and flanges 5 and also
the opposed lateral recesses have been filled out with board
strips 10 and 11, respectively, This wil] make for good
thermal insulation of the joint,
A second embodiment of a roofing e]ement according to
the invention is illustrated in Fig, 5, This element has
spaced upper and lower skins 1, 2 like those already described
in conjunction with ~ig, 1, whereas the intermediate beam
members are box-like structures having lateral webs 4 of
board strips joined to wooden members 5 corresponding to
the I-beam flanges 5, ~he internal spaces of the beams are
fil~ed out with an insulating material, as are, although
not illustrated, the spaces defined between the webs 4 and
the skins.
In ~ig, 6 there is illustrated a joint between two roof-
ing elements of the kind described in the foregoing para-
graph. In this e~ample the upper skin of both elements
covers only about half the width of the outermost beam
members, The actual juncture between the elements is covered
by a longitudinal strip, Insulation 10 may also be fitted
between the adjoining lateral faces,
A roof constructed of elements according to the invention
must be covered by a protective layer, such as roofing felt,
plastic or sheet metal, This layer has no load-carrying
function, since the roofing elements are rigid in themselves,
The roof is protected against fire by the metal sheeting
at its underside, and this sheeting also forms an effective
barrier against the diffusion into the element of humidity,
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~ he number of beam members for each roofing element is
dependent on the width of the element. It may be five for
a width of about 2,4 meters, A standard width is 1,2 meters,
when three beam members are provided. lhe upper skin may
consist of chip boarding or other wood-based board material
instead of plywood.
The invention is not restricted to the specific embodi-
ments described and illustrated but can be varied and
modified within the scope of the appended claims.
