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BACKGROUND OF THE INVENTION
1. Field of the Invention:
This invention relates to cold formed, sheet metal, profiled building units
such as those useful as floor, wall or roof elements or other structural
elements, and more particularly to improvements in such profiled building
units and method for making the same.
2. Description of the Prior Art:
Roll formed sheet metal decking units currently present integral
embossments, indents and formed ribs that interlock with a layer of
concrete poured thereover to provide a composite floor slab. Such sheet
metal decking units have been produced for more than twenty-five years and
have been used in hundreds of millions of square feet of composite floor
slabs.
Such decking units typically present flat regions, such as, alternating
crests and valleys and sloped webs connecting adjacent ones of the crests
and valleys. Since the sheet metal used to produce the decking unit has a
substantially uniform thickness and since the decking units are roll
formed, the crests, the valleys, the webs and the longitundinal stiffening
ribs also are essentially of substantially the same uniform thickness with
some minor localized stretching occurring at the outer periphery of the
radii portions and minor localized compressing occuring at the inner
periphery of the radii portions. In current roll forming practice, the
smaller individual intermittent indents and embossments of composite
decking units are stretched-in.
One of the earliest roll formed decking units exhibiting composite
characteristics, utilized only embossments or their equivilents in the
webs, see SHEA U.S. Pat. No. 3,397,497.
A later roll formed composite decking unit utilized longitundinal ribs in
the crests and in the webs as well as embossments in the webs and in the
valleys to provide a decking unit having improved "wet strength" and
"composite characteristics" superior to those of the SHEA '497 decking
unit, see for example ALBRECHT et al. U.S. Pat. No. 3,812,636. Other
recent examples of such roll formed composite sheet metal decking units
will be found in WASS U.S. Pat No. 4,144,369; TING U.S. Pat. No.
4,453,364; and STOHS U.S. Pat. No. 4,726,159.
Other building units having flat regions requiring stiffening against
buckling, include corrugated roof deck, and wall structure elements such
as profiled facing sheets and liner sheets. The prior art is replete with
examples of such building units.
Currently the building units, such as, facing sheets, liner sheets, and
decking units; and individual structural elements, such as, hat-shaped
subgirts of various depths are roll formed by passing a sheet metal strip
of uniform thickness through successive stands containing forming rolls
wherein the sheet metal strip is reshaped incrementally into the desired
profile. As the strip travels through the roll forming apparatus, the
opposite sides of the sheet metal strip are freely drawn-in laterally to
provide sheet metal for forming the overall profile and the longitudinal
ribs. The free lateral draw-in of the sheet metal is desired to avoid
stretching or tearing of the sheet metal, see for example COOKSON U.S.
Pat. No. 3,184,942; CAMPBELL U.S. Pat. No. 3,256,566; and COOKSON U.S.
Pat. No. 3,690,137.
Thus designers of building units must utilize sheet metal strips of a width
sufficient to provide not only for the profile itself but also for the
stiffener ribs formed in the various flat regions of the building units.
Similarly, designers of individual structural elements must utilize sheet
metal strips of a width sufficient for the desired profile. Since the cost
of the sheet metal used to produce these components comprises a very high
percentage of the total product cost, efficient utilization of the sheet
metal in the design of these components is most important. Heretofore with
regard to building units, a savings in the sheet metal usage could be
achieved by eliminating one or more of the stiffening ribs, by reducing
the depth of the decking unit, or by using a lighter gauge sheet metal.
With regard to the individual structural elements, a savings in the sheet
metal usage could be achieved by reducing the depth of the element or by
using a lighter guage sheet. The resultant savings were balanced against
the loss in strength and span capability of the building unit. More often
than not, no changes were made or at most very minor changes were made.
BRIEF SUMMARY OF THE INVENTION
The principal objects of this invention are to provide improved cold
formed, sheet metal, profiled building units and a method of making the
same.
Another object of this invention is to provide a profiled building unit
having longitudinal stiffener ribs that are stretched-in thereby resulting
in a savings in the weight of metal required per unit of cover width.
Still another object of this invention is to provide a method of making the
present profiled building unit, which method when accomplished by roll
forming apparatus, achieves a reduction in the number of stands required
to roll form the present profiled building unit.
A still further object of this invention is to provide a sheet metal
structural element having a U-shaped central portion or stiffening rib
that is formed by stretching a segment of the sheet metal strip from which
it is formed.
In its broadest aspects, the present invention provides improvements in
cold formed, profiled building units of the type used as floor, roof or
wall elements. The profiled building unit is formed from a sheet metal
strip of substantially uniform sheet thickness and having at least one
flat region that is subject to buckling under compressive forces. Examples
of such flat regions include the crests and the valleys of profiled floor
deck and roof deck, and of profiled facing sheets used as the exposed face
of wall and roof structures; and the flat central web of liner sheets used
as the interior face of wall structures.
In accordance with the present invention, at least one stiffening rib is
formed in the flat region. The rib extends along substantially the entire
length of the flat region and has a substantially uniform rib thickness
that is less than the uniform sheet thickness of the sheet metal strip.
The flat region on opposite sides of the stiffening rib has a thickness
substantially equal to the uniform sheet thickness of the sheet metal
strip. In accordance with known principles of sheet metal design, the
number of stiffening ribs formed depends on the width/thickness ratio of
the flat region.
In another of its aspects, the present invention provides improvements in
cold formed structural elements, such as, a hat-shaped subgirt. The
structural element has a U-shaped central portion or stiffening rib that
provides the stiffness and stregth of the structural element.
In accordance with this invention, the stiffening ribs are formed not by
being drawn-in as in current roll forming practices but, instead, by
stretching a segment of the sheet metal strip. As a result of being
stretched-in, the stiffening ribs each have a substantially uniform rib
thickness that is less than the uniform thickness of the sheet metal; and
a profile width, as measured along the centerline of the rib, that is
greater than the linear width of the segment from which it was
stretched-in. The overall arrangement is such that narrower sheet metal
strips are used to form the present building units and the structural
elements, since it is not necessary, as in current roll forming practice,
to allocate sheet metal girth for the formation of the stiffening ribs.
These and other objects and advantages of the invention will become
apparent from the following description with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a flow diagram schematically illustrating roll forming of a
profiled sheet metal decking unit according to the prior art;
FIG. 2 is a flow diagram schematically illustrating roll forming of a
profiled sheet metal decking unit according to the present invention;
FIG. 3 is a fragmentary perspective view of an embodiment of the sheet
metal decking unit of this invention;
FIG. 4 is an end view of a further embodiment of the sheet metal decking
unit of this invention;
FIG. 5 is fragmentary isometric view of forming rolls used in a first roll
forming stand according to this invention;
FIGS. 6 and 7 are fragmentary cross-sectional views, taken transversely
through forming rolls, illustrating the two-step stretch-in of a
stiffening rib;
FIGS. 8A and 8B are end views of the left-hand side and the right-hand
side, respectfully of the sheet metal strip as it emerges from rolls of
FIG. 5;
FIGS. 9 to 14 are fragmentary, transverse cross-sectional views of
stiffening ribs;
FIGS. 15 and 16 are cross-sectional views, taken transversely through a
valley, illustrating the two-step stretch-in of a valley stiffening rib;
FIG. 17 is an enlarged view of a flute and the adjacent valleys of a
further embodiment of a decking unit of this invention;
FIG. 18 is an end view of a further embodiment of the present sheet metal
decking unit;
FIG. 19 is an end view of a cellular floor deck unit;
FIG. 20 is an end view of a hat-shaped roof deck unit;
FIGS. 21 to 29 end views of typical profiled sheets used in sandwich
constructions, such as, walls or roofs;
FIG. 30 is a flow diagram schematically illustrating roll forming of a
structural element according to the present invention; and
FIG. 31 is an end view of the structural element formed in FIG. 30.
DESCRIPTION OF THE PREFERRED EMBODIMENT(s)
Referring to FIG. 1 there is shown a flow diagram 30 schmetically
illustrating the profiling of a sheet metal strip 32 to produce a decking
unit 34 according to roll forming practices of the prior art. FIG. 1
illustrates only one-half of the decking unit 34. The opposite half is
essentially a mirror image of that half shown in FIG. 1 and differs only
in having a male marginal connector (not visible) that cooperates with the
female marginal connector 36 (FIG. 1) of an adjacent decking unit to
connect the two units together. The decking unit 34 is of the type
described and claimed in the aforesaid ALBRECHT et al., U.S. Pat No.
3,812,636, and, as illustrated, requires a twenty-seven roll forming
stands.
As can be seen, the decking unit 34 includes a central flute 38, a lateral
trough 40 adjacent thereto, a lateral flute 42 adjacent to the trough 40,
and a partial valley 44 which includes the female marginal connector 36.
As can be seen in FIG. 1, the central flute 38 is essentially completely
formed at about roll forming stand No. 5. Formation of the lateral trough
40 is accomplished from roll forming stand No. 6 through roll forming
stand No. 10. The formation of the lateral flute 42 begins at roll forming
stand No. 6 and is essentially complete after roll forming stand No. 17.
Formation of the partial valley 44 begins at about roll forming stand No.
18 and is completed at roll forming stand No. 27.
As can also be seen in FIG. 1, the decking unit 34 has at least one
longitudinal stiffening rib 46 formed in the central crest 48 of the
central flute 38 at the first roll forming stand No. 1. The decking unit
34 also includes stiffening ribs 50, one each formed in the webs 52.
Formation of the first rib 50 commences at roll forming stand No. 2,
formation of a second stiffening rib in the adjacent web 52 commences at
roll forming stand No. 7, and formation of a third stiffening rib 50 in
the web 52 commences at roll forming stand No. 13. Another longitudinal
stiffening rib 46 is started in the lateral crest 54 of the lateral flute
42 at roll forming stand No. 11. In roll forming stand No. 20, a plurality
of transverse embossments 56 are formed in each of the valleys 58 of the
lateral trough 40 and of the partial trough 44.
According to current roll forming practices, the longitudinal stiffening
ribs 46 and 50 are formed by laterally drawing-in the sheet metal strip
32. Thus when designing sheet metal decking units, such as the unit 34,
sheet metal girth must be allocated for the formation of the ribs 46, 50.
Referring now to FIG. 2, there is shown a flow diagram 70 schematically
illustrating the profiling of a sheet metal strip 72 to produce a decking
unit 74 according to the present invention. The metal strip 72 may
comprise steel, aluminum, zinc or other ductile metals or metal alloys.
FIG. 2 illustrates only one-half of the decking unit 74 and it should be
understood that the opposite half is essentially a mirror image of the
half shown in FIG. 2. As illustrated in FIG. 3, the decking unit 74 has
marginal connectors along the opposite longitudinal edges thereof which
comprise, for example, a male lip 76 and a female lip 78 which are adapted
to interconnect with a female lip 78 and a male lip 76 of adjacent decking
units 74 to connect the units together. The decking unit 74 presents
alternating crests 80 and valleys 82, and sloped webs 84 connecting
adjacent ones of the crests 80 and the valleys 82. The decking unit 74
presents a central flute 86 consisting of a central crest 80 and the
adjoining sloped webs 84; lateral troughs 88 each comprising one of the
valleys 82 and the adjoining sloped webs 84; and lateral flutes 90 each
comprising one of a lateral crest 80 and the adjoining sloped webs 84.
Each of the crest 80 is provided with at least one and preferably two
longitudinally extending first stiffening ribs 92; the lateral valleys 82
each are provided with at least one longitudinally extending second
stiffening rib 94; and each of the sloped webs 84 is provided with at
least one longitudinal extending third stiffening rib 96. The ribs 92, 94
and 96 extend along substantially the entire length of the decking unit
74. In order to further enhance the composite co-action between the
decking units 74 and an overlying layer of concrete, each of the sloped
webs 84 is provided with a plurality of transversely extending embossments
98. In order to strengthen each juncture 103 between the sloped webs 84
and the crests 80 so as to better resist impact loads due to construction
traffic, a longitundinal rib 105 is provided immediately adjacent to each
juncture 103. The stiffening ribs 105 preferably are provided in the
crests 80 as illustrated in FIGS. 3 and 17, but, alternatively, may be
provided in the webs 84 immediately adjacent to each juncture 103.
FIG. 3 illustrates the decking unit 74 having three flutes 90, 86 and 90
and two troughs 88, 88. A commercial embodiment of the decking 74 would
have coverage width of 36" (91.44 cm). FIG. 4 illustrates a narrower
decking unit 74' having two flutes 90, 90 and one central trough 88'. A
commercial embodiment of the decking unit 74' would have a coverage width
of 24" (60.96 cm). The first, second and third longitudinal stiffener
beads 92, 94 and 96 are formed in the sheet metal strips 72 (FIG. 3) and
72' (FIG. 4) in first, second and third regions corresponding,
respectively, to the crests 80, the valleys 82 and the webs 84.
In one mode of practicing the present invention, the first roll forming
stand receives the sheet metal strip 72 as a flat sheet and while the
strip 72 passes therethrough, forms the embossments 98 and the third
stiffening ribs 96 in the third longitudinal regions of the strip 72 which
will correspond to the sloped webs 84. In addition, it is preferred that
the first stiffening ribs 92 (only one visible in FIG. 2) be provided in a
central region of the strip 72 which will correspond to the central crest
80 (FIG. 3).
As shown in FIG. 5, the roll forming stand No. 1 utilizes upper and lower
rolls 100, 102, of which only one-half are illustrated. The rolls 100 and
102 are symmetrical about the vertical axis 104. The rolls 100, 102 are
provided with a cooperating rib 106 and groove 108 for forming the first
stiffening rib 92; with a plurality of cooperating rib and groove
formation 110, 112 for forming the third stiffening ribs 96; and with
circumferentially spaced projections 114 on the lower roll 102 and with
cooperating circumferentially spaced recesses 116 on the upper roll 100
for forming the embossments 98.
In another mode of practicing the present invention, a third stiffening
ribs 96' could be formed by passing the sheet metal strip 72 through two
consecutive roll forming stands as shown in FIGS. 6 and 7. FIG. 6
illustrates fragments of upper and lower rolls 142, 144 which introduce a
relatively shallow S-bend into the sheet metal strip 72, such S-bend being
wider and shallower than the completed S-bend in forming the stiffening
rib 96' of FIG. 7. Thus the material is stretched over a wider area,
providing adequate girth for the completed S-Bend of the stiffening rib
96' at a lesser percentage of stretch. FIG. 7 illustrates fragments of
upper and lower rolls 146, 148 which form the rib 96' with the rib-like
projections 96A', 96B'. The two-step formation of the rib 96' as
illustrated in FIGS. 6 and 7 is preferred when the sheet metal strips 72
of less ductile metals are used.
With references to FIGS. 8A and 8B, it should be noted that the outermost
third stiffening ribs 96E adjacent to the opposite ends 118, 120 of the
sheet metal strip 72 serve to restrain the portion of the sheet metal 72
therebetween against being laterally drawn-in toward the centerline 104.
The stiffening ribs 96E are considered to be formed by drawing-in portions
of the sheet metal strip 72. While in actual practice some stretching does
occur in the formation of the stiffening ribs 96E, only the first
stiffening ribs 92 and the four intermediate third stiffening ribs 96 are
considered to be formed by stretching segments of the sheet metal strip 72
and as a result each have a substantially uniform rib thickness that is
less than the uniform thickness of the sheet metal strip 72.
As can be seen, for example, in FIG. 9, the first stiffening rib 92 is
formed from a segment illustrated by the dash-dot line 93 of the sheet
metal strip 72. The segment 93 has linear width LW. When formed, the first
stiffening rib 92 has a profile width PW (as measured along the centerline
of the rib 92) which is greater than the linear width LW of the segment
93.
Likewise, as shown in FIG. 10, for example, the second stiffening rib 94 is
stretched-in from a segment illustrated by the dash-dot line 95 of the
sheet metal strip 72. The segment 95 has a linear width LW. When formed,
the stiffening rib 94 has a trapazoidal configuation and a profile width
PW (as measured along the centerline of the rib 94) which is greater than
the linear width LW of the segment 95.
As an alternative, a second stiffening rib 99 (FIG. 11) may be provided,
having an arcuate configuation similar to that of the first stiffening rib
92 (FIG. 9). The stiffening rib 99 is stretched-in from a segment
illustrated by the dash-dot line 101 of the sheet metal strip 72. The
segment 101 has a linear width LW. When formed, the stiffening rib 99 has
profile width PW (as measured along the centerline of the rib 99) which is
greater than the linear width LW of the segment 101.
Likewise, as shown in FIG. 12, for example, the third stiffening rib 96 is
formed from a segment illustrated by the dash-dot line 97 of the strip
72--the segment 97 having a linear width LW. When formed the third
stiffening rib 96 has a profile width PW which is greater than the linear
width LW of the segment 97. Alternatively, the third stiffening rib may
take the form of an outwardly projecting rib 150 (FIG. 13) or an inwardly
projecting rib 152 (FIG. 14) each of which is formed by stretching a
segment illustrated by the dash-dot line 154 of the strip 72. When formed,
the ribs 150, 152 each have a profile width PW which is greater than the
linear width LW of the segment 154.
It will be appreciated that the savings in the overall sheet metal girth
corresponds to the sum of the differences between the profile widths PW
and the linear widths LW of the stiffener ribs used in the building unit.
As can best be seen in FIG. 12, the third stiffening rib 96 has an S-shaped
configuration including rib-like projections 96A, 96B projecting from
opposite sides of the sloped web 84. The rib-like projection 96A projects
away from the flute 86, 90 and thus positioned serves as a nesting bead on
which the next higher decking unit will rest. The stacked decking units
are precluded from jamming together. Thus the decking units are fully
nestable in jam-free relation for packaging, storage and shipment.
Reverting to FIG. 2, as the sheet metal strip 72 passes through roll
forming stand Nos. 2 through 5, the central flute 86 is formed.
Thereafter, formation of the lateral trough 88 commences at roll forming
stand No. 6 and is essentially complete at after roll forming stand No.
10. Formation of the lateral flutes 90 commences at roll forming stand No.
11 and is completed at about roll forming stand No. 19.
It will be observed that a longitudinal second stiffening rib 94 is formed
in the valley at roll forming stand Nos. 12 and 13. The two-step formation
of the second stiffening rib 94 is best illustrated in FIGS. 15 and 16. In
FIG. 15 there is illustrated upper and lower rolls 122, 124, respectively.
The upper roll 122 presents a pair of circumferential grooves 126 which
cooperate with a pair of circumferential ribs 128 to provide initial
stretching of the segment 95 (FIG. 10) of the valley 82 to produce the
sinuous profile 130. The sheet 72 continues to roll forming stand No. 13
where, as shown in FIG. 16, there is presented upper and lower forming
rolls 132, 134, respectively. The upper roll 132 presents a
circumferential depression 136 which cooperates with the circumferential
rib 138 to produce the final stretch-in of the second stiffening rib 94.
Reverting to FIG. 2, it will be observed that additional longitudinal first
stiffening ribs 92 are stretched-in in the crests of the lateral flutes 90
at roll forming stand No. 19, in the manner hereinbefore described.
FIG. 17 illustrates a further embodiment of the present decking unit and is
designated generally by the numeral 75. The decking unit 75 incorporates
the second stiffening ribs 99 of FIG. 11, in those valleys 82 disposed
between adjacent ones of the crests 80. Plural embossments 140 may be and
preferably are formed in all of valleys 82. In those valleys 82 containing
a stiffening rib 99, the embossments 140 are provided on each side of the
rib 99. The embossments 140 extend transversely of the valleys 82 and
serve as concrete keying elements that cooperate with the embossments 98
in the webs 84 to resist sliding and separation of the decking unit 75
from an overlying layer of hardened concrete (not shown) when the decking
unit/concrete combination is subjected to shear forces.
FIG. 18 illustrates a still further embodiment of the present decking unit
and is designated generally by the numeral 77. In the decking unit 77, the
crests 80 and those valleys 82 disposed between adjacent ones of the
crests 80, each incorporate at least one of the stiffening ribs 94 whereas
the sloped webs 84 incorporate the stiffening ribs 96.
The present invention is also applicable to other building units, such as,
cellular floor deck, roof deck and the liners and facing sheets of wall
structures.
FIG. 19 illustrates a cellular decking unit 156 formed from a corrugated
upper metal sheet 158 and an essentially flat lower sheet 160. The upper
metal sheet 158 presents flat regions or crests 162 each provided with a
stretched-in stiffening rib 164. The lower metal sheet 160 is provided
with stretched-in stiffening ribs 166 which serve not only to strengthen
and stiffen the wide flat expanse of the lower sheet 160 but also to
position the upper sheet 158 with respect to the lower sheet during
welding of the two sheets 158, 160.
FIG. 20 illustrates a hat-shaped roof deck 168 presenting a flat region or
crest 170 provided with a stretched-in stiffening rib 172.
FIGS. 21 and 22 illustrate profiled sheets 174, 176 presenting flat regions
or central webs 178, 180. The central web 178 of the liner 174 is provided
with a single stretched-in stiffening rib 182. The wide central web 180 of
the sheet 176 is provided with three substantially uniformed spaced,
stretched-in stiffening ribs 184.
FIGS. 23, 24 and 25 illustrate profiled sheets 186, 188 and 190 used in
single sheath structures or in double-sheath wall structures.
The profiled sheet 186 (FIG. 23) is corrugated and presents flat regions or
crests 192 each provided with a stretch-in stiffening rib 194.
The profiled sheet 188 (FIG. 24) presents an outboard flat region or crest
196 and an inboard flat region or valley 198. The crest 196 and valley 198
are of substantially the same width and thus each is provided with a
single stretched-in stiffening rib 200.
The profiled sheet 190 (FIG. 25) presents an outboard flat region or crest
202 and an inboard flat region or valley 204. Since the crest 202 is twice
as wide as the valley 204, the crest 202 is provided with two spaced-apart
stretched-in stiffening rib 206. The valley 204 is narrow enough that no
stiffening rib is required.
FIGS. 26 to 29 illustrate profiled sheets 208, 210, 212 and 214 used in
single sheath structures or in double sheath wall structures.
The profiled sheets 208 and 210 (FIGS. 26, 27) present plural flat regions
or crests 216. The profiled sheets 212 and 214 (FIGS. 28, 29) have
relatively wide flat regions or valleys 218. In accordance with the
present invention, the crests 216 and valleys 218 can be provided with one
or more stretched-in stiffening ribs represented by the dotted
half-circles numbered 220 without having to increase the width of the
sheet metal strip from which the profiled sheets 208 to 214 are formed.
It is to be understood that all of the stiffening ribs 164, 166, 172, 182,
184, 194, 200, 206 and 220 of FIGS. 19 to 29 extend longitudinally and
substantially the entire length of the associated building unit.
The present invention also provides improvements in a method of making
building units described herein; and building units, not specifically
illustrated herein but intended to be encompassed by the claims, that
incorporate not only the combinations illustrated but also other
combinations of the stiffening ribs described herein in the longitudinal
flat regions of the building units.
The method of the present invention also applies to building units
incorporating stiffening ribs of any configuration which have been formed
not by being drawn-in as in current roll forming practices, but, instead,
by being stretched-in as disclosed in this specification.
The present invention provides improvements in the method of profiling a
sheet metal strip that has a substantially uniform thickness and that is
provided in a preselected width. The method provides a cold formed
building unit such as a floor, roof or wall element illustrated in FIGS.
3, 4 and 17 t | | |
