Note: Descriptions are shown in the official language in which they were submitted.
~AC~C~rU~D or l~r l~v~rlo~
The use o~ in~umescent material in cable ducts, for
the purpose of preventing ~he duct rom, in effect, becoming a
flue for the transmission of smoke, heat and flame from one area
to another, is known. Thus, for example, in non-ventilated cable
raceways, such as in the so-called under;flovr duct commonly used
to house cables, telephone lines, electrical wires, etc., in
office and apax~nent buildings, where it is d2sired to help pre-
vent transmis~ion of damaging effec1:s of fire within h~ raceway
lG from one section of the building to another, intumescent materi~ls
are known to have been utilized.
By an intumescent material is meant one which enlarges,
swells or bubbles upon exposure to heat above pre-determined
levels. Thus, for example, so-called "FL~M~REST 1600", as mar-
keted by Avco Systems Division o ~owell, Massachusetks, is an
intumescent, epoxy coating, containing an intumescent component
designed for both interior and exterior use and many industrial
applications. It is a two-component, catalyzed, epoxy resin
which fuses into a porcelain-like shield to protect the substrate
while providing a highly efficient barrier against flame and heat.
Typically, such coatings may be applied in a thickness
of 20 to 25 mils. As the coating is exposed to heat at a pre-
selected level, for example, 500F, the resin softens and the in-
tumescent material begins to change state and evolves from a high
.~ density film to a low density "intumescent char", wherein a
multiplicity of air cells in the char act as insulators and keep
the substrate cool. As an intumescent mechanism, the foregoing
phenomenon may be completed in a matter of seconds, for example,
30 seconds or so, after the coatin~ is exposed to heat and/or
fire~ By positioning such material in a confined passageway,
such as the interior of a cable raceway, it is possible to have
the intumescent char traverse the cross~section of the passageway
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such that, upon completion of the heat exposure cycle of the
intumescent material, the passageway becomes effectively blocked.
This concept has been adopted in the design of enclosed under-
floor ducts, for example, as hereinbefore described.
In addressing the question of utilizing intumescent
material in generally open, ventilated devices such as cable
trays, it mus~ be kept in mind that the problems involved are
significantly differenk than those in generally non-ventilated
structures, such as cable raceways and the like. `
Typically, one form of cable tray is made as a flat,
hung-suppor~ member, having a multiplicity of holes for the lib-
eral convection of air therethrough, so that heat generated in
the cables in the normal course of use may be easily and adequately
dissipated, However, this very feature of enhancement of con-
vection in normal circumstances becomes undesirable in extreme
cases such as fire in the ambient region in which the trays are
located because, inherently, it tends to enhance the passage of
heat and flame into, through and around the areas in which the
cables are positioned. In the past, where the consequences of
; 20 destruction of cables due to these phenomena were mainly mere
power losses, concern was somewhat less than now, when the des-
truction of cables can have the effect of rendering inoperative
control, servo, and other mechanisms and devices, which may be
critical to health or safety, as, for example, reaction control
devices, in nuclear-reactor installations. It might be thouyht
that to address this problem by coating the inside of the holes
in such cable trays with intumescent material, would suffice, with
the idea that upon exposure to heat, the material would expand
and shut off the convective paths. However, the heat from a
fire in an ambient region can be so intense, and the consequent
; "flue effect" through the ventilating holes in a direction no~-
mal to the tray can be so pronounced, that by the time a sufficient
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amount of time has passed for the intumescent material to begin
to react to the sudden heat rise, the rate of convection through
the holes, coupled with the relatively fragile "char" state of
the intumescent material as it approaches its fully expanded con-
dition, can cause the blocking to be inhibited, or e~en totally
precluded.
Accordingly, it is an object of this invention to pro~
vide a means for selectively and automatically restricting the
flow of heated air through ~tructures, which are intended to
encourage free ventilation under usual circumstances.
Another object of this invention is to provide such
means in a fashion most likely to achieve effective restriction
of the flow of heated air under extraordinary conditions.
Yet another object of this invention is to provide
means to satisfy the foregoing objectives, which is structurally
sound from an engineering standpoint for its intended functional
use, such as supporting ca~les, and, at the same time, is struc
turally simple and comparatively inexpensiYe to produce,. : 3
Still another object of this invention is to provide
means to satisfy the foregoing ob~ectives using materials and
stxuctures which are reliable and ef~ective.
SUMMARY OF THE INVENTION
.
Desired objectives may be achieved through practice
of the present invention, one em~odiment of whi¢h comprises a
structure having walls secured in spaced-apart relationship with
respsct to each other, in which air and/or gases may pass between
convection holes in one of the walls and convection holes in the
other of the walls, the holes in one wall not being aligned with
the holes in the other of the walls. Intumescent material is
positioned in the passageway betwe~n the holes in ea~h of the
walls for obstructing the flow of air therebetween upon thermal
activation. Another embodiment of this invention comprises
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such a structure wharein the walls deinin~ the passageway are
the double floor mambers of the cable tray device, and further
embodiments in which one or both of the floor members are of
the so-called "corrugated" construction. Unperforated portions
of the structure are positioned substantially opposi~e t~e con-
vection holes in at least one of the walls such that intumescent
material may form a char between the hole and the unperforated
portion,
DESCRIPTION OF DRAWINGS
10This invention will be clear from the description which
follows and from the accompanying drawing~ in which
Figure 1 is a plan view of an embod~ment of this in-
vention;
Figure 2 i~ a cross-section o the ambodiment of this
invention as shown in Figure 1 taken along section line 2-2;
Figuxe 3 is a cross-section of the embodiment of this
invention shown in Figure 1 taken along ~ection line 3-3;
Figure 4 is a cross-section vie~ of another embodiment
of this invention;
20Figure 5 is a cross sectional view of yet another em-
;~ bodiment of this invention;
Figure 6 is a cross-sectional view of yet another em~
bodiment of this invention;
Figure 7 is a cross-sectional view of still another em-
bodiment of this invention;
Figure 8 is a cross-sectional view of still another
embodiment of this invention; and
Figure 9 is a cross sectional vi~w of still another em-
bodiment of this invention; while
30Figure 10 illustrates an installation application for
an embodiment of this inventionO
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DF,SCRIPTION OF RREFERRED EMBODIMENT
Referring firs~ to Figures 1 through 3, ~h~re is de-
picted an embodiment of this invention useful for use as a cable
tray support device com~risin~ a floor section having two com- -
ponent layers 12, 14. As may be seen particularly in Figure 1,
the upper floor member 12 includes rows of convection holes 30
30a, 30b, ..~ 30n; 32, 32a, 32b, ... 32n; ...(etc~) oriented
substantially normal to the long axis of the structure. Similarly~
the lower floor member 14 has rows of holes 20, 20a, 20b ~., 20n;
22, 22a, 22b, .... 22n ..... (etc.) which are also oriented substan -
tially normal to the long axis of the device. It will be noted par-
ticularly from Figure 2 ~hat the upper floor member 12 is "corrugated"
As there illustrated, ~hese corru~ations are substantially "U"
shaped in cross-section, since this is a usual structural feature of
cable tray devices. It should be understood, however, that al-
though such U-shaped corrugations are shown here for purposes of
illustration, corrugations of other configurations, such as tri-
angles, elipses, sinusoids, etc., may be also or alt~rnatively
, ~ be utilized withou~ departing from the spirit or scope of this
in~ention.
Referring to Figure 2, it will be se~n that the top
member 12 is made in a cor~ugated configuration with ~ands or
peaks 15 and grooves 16, and that in this particular configuration,
the grooves 16 have holes 30 positioned therein. Correspondingly,
the lower floor member 14 has peaks or lands 18 and grooves 19
the latter of which have holes 20 therethrough. It will be noted
further, particularly from Figure 2, that the corrugations of one
of the layers are substantially paxallel to the corrugations of
the other layers, with the peaks of each positioned substantially
opposite the peaks of the other, and with the ~alleys of each
positioned substantially opposite the vall~ys of the other~ By
such juxtapositioning of such floor mem~ers, it will be further
seend particularly from ~gure 2, tha~ as between floor members
the hole sequence alternates; that is, proceeding from left to
righ~ substantially at right angles to ~he axial lines of the cor~
rugations, one comes first to a hole in the lower floor member,
and then to a hole în the upper floor member, and so forth. Thus,
it will be clear that, as between the two floor members, the holes
in them respectively form convection passageways which are tortuous;
that is~ tend not to be ~trai~ht but instead, are along devious
paths, since the holes in one of the members are out of alignment
10 (i.e. O not positioned opposite) the holes in the okher of the
members.
Figure 3 further il~ustrates this embod~ment of the pre-
sent invention, showing, in addltion, hangar~3 24, by which the dou-
ble floored structure may be suspended, a~0 for example, from
supporting trusses or other known per se ~upport members tnot
shown).
Turning now to Figure 4, ~here is illustrated in greater
detail a cros~-section of the embodiment shown in Figure 2. In ~ ~:
addition to the structural eatures shown in Figure 2, Figure 4
illustrate~ the further application of an intumesaent material
7 on the upper side of the lower floor member, i.e. on the in-
side of the pas~ageways between the holes 30 of the upper ~loor
member and the holes 20 of the lower floor member. By this means,
the normal convective flow path (A) of air through the cable tray
device which, as is known, has a beneficial cooling effect on the
cables 5 being supported on the top of peaks 15 of the upper floor
member 12, may, upon the application of heat, be caused to be-
come closed when the intumescent material 17, reacting to the
heat, turns into intumescent char 9. This phenomena may be seen
to have effecti~ly closed off the pa~sageway between the groove
hole 30 in the upper floor members 12 and the convection hole ~0
in the lower floor member 14~ This phenomena, repeated along
a substantial portion of the entire tray length will, o course,
have the effect of reducing the thermal exposure of the cables,
therefore causing them at least to remain operative for a substan~
tially longer period of time, and perhaps even to survive totally
an exposure that might otherwise cause them to fail It should
be noted in particular that in the embodiment shown in Fi~ure 4,
assuming that the most immediate exposure to fire in the ambient
environment is at the underside of the under-floor member 14, the
intumescent material 7, particularly in the area above the valley
18 of the lower floor member 14~ may be expec~ed to react quickly
to the exposure to flames on the tray floor member 14 of heat
; transmitted conductively to the region where the intume~cent mat~
erial is positioned immediately below the hole 30 in the bottom
of the valley o the upper floor member 12. Thus, this relatively
~ rapid time response, as well as the structural feature of having
the int~mescent material, as it changes towards becoming intum-
escent char 9, firmly positioned and supported on the upper side
of the valley 18 in the lowex floor member 14, as a support base,
tends to minimize the "flue effect" which might oth~rwise occur.
, ~ 20 For applications such as are discussed here, the space between
the two floor members may be typically rom, say 1/8" to 1".
Preferably the space will be selected to permit adequate ventila-
tion air flow under normal circumstances but will permit the in-
tumescent char to obstruct air and gas passage under extreme cases
when the char i5 formed.
: Figure 5 illustrates another embodiment o this invention.It will be seen that the upper floor member 12 in this embodiment
corresponds to the upper floor member 12 shown in Figure 4. How-
ever in the embodiment shown in Figure 5, the lower floor member
- 30 50 has peaks 52 and grooves 54, in the bottom o which grooves
are positioned holes 56. Thus~ passaget~ays for the flow of air
along path (A) are effectively defined between the holes 56 in
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the valleys of the lower membex S0 and the holes 30 in the valleys
of the upper member 12. As is the case with the embodiment
shown in Figure 4, the reaction time of the intumescent material
to heat applied to the underside of the lower
floor member 50 should be expected to be relatively rapid because ~ !
of the ahility of the ma~erial of the lower floor member 50 to
transmit heat and thereby cause the generation of intumescent char
9 to block the passageways between holes. ~owever, it will also
be noted that in this embodiment, the width and alignment of the
upper side of ~he valleys 54 of the lower floor member 50 are
such that they do not provide as broad a structural support member
for the generated intumescent char 9 as is the case with an
embodiment like that shown in Figure 4. Turning now to Figure 6,
there is illustrated an embodiment of the present invention having
a lower floor member substantially corresponding to that shown in
Figure 5. However, in the embodiment shown in Figure 6, the upper
floor member 60 has valleys 64, and peaks 62 in which are posit-
ioned the holes 66. Thus, in this embodiment, the effective
convective passageway for air is illustrated as being along the
flow path (A) from holes 56 in the grooves of the lower floor mem-
ber 50 to holes 66 in the peaks of the upper floor member 60. It
will also be apparent that although, in this embodiment, the upper
side of the grooves 54 in the lower 100r member 50 provide a
better structural support for the generated intumescent char 9
than that shown in Figure 5 and can be expected to exhibit similar
thermal conductivity and therefore intumescent char actuation
characteristics as the embodiment shown in Figure 5, the structural
support characteristics for the intumescent char are better than
those shown in Figure 4.
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Figura 7 illustrates an embodiment of this invention
having an upper floor member 60 with elements substantially cor-
responding to the upper floor m~mber illustrated in Figure 6,
along with a lower floor member 14 having structural characteris-
tics substantially corresponding to the lower floor member shown
in Figure 4. It will be apparent ~hat in the embodLment of this
invention shown in Figure 7, al~hough the thermal actuation through 3
conduction may be expected ~o be subs~antially as fast as that
; which can be expected to be experienced with the embodiment shown
in Figure 4, the structural support for the generated intumescent
char 9 is not as broad or well posi~ioned as that shown in Figure
: 4.
Thus, from the foregoing, althou~h it will be understood
that the embodiments shown in Figures 4, 5, 6 and 7 all fall
within the contemplation of this invention, it is believed that
the embodiment shown in Figure 4 may be expected to prove to be
the most significant technically as well as commercially because
of the comparative speed with which its intumescent material
will be actuated and the structural features it provide~ by way of
char support and passageway configuration, with consequent attenu-
a~ion of "flue effect
Further, from the foregoing, it will be apparent that theprincipals of this invention may find application in a wide var-
iety of structural embodiments other than cable trays of the con~
figuratlon hereinbefore described. ~hus~ for example, a relatively
simple panel insert, not necessarily designed to be a cable tray
per se or to be used only with cable tray , may be made of paral-
lel, separated wall members with non-align~d holes, to act as an
intumescen~ barrier to an otherwise ~luid tran5missive structure,
or as a flame gas~ and the like barrier for other structures as shown
in Figure 10~ Thus, it may be used as a vertical wall panel, or
as a slab-like floor member to be dropped in the bottom of a
,
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cable tr~y or other normally conv~ctive permissive structure.
Similarly, although the protected device, such as the cables here-
inbefore described~ may be positioned in the convec tive top-most
position (e.g., atop the top member of a cable tray), they may
also be positioned between the upper and lower floor members,
even though the exposure to conductive heating may be somewhat
greater, since in such an intermediate posture, ultimate surxounding
by char can have substantially similar heating inhibitin~ effect,
with conse~uent preservation benefits. Further, it will be
apparent that the desired effect of providing a good oundation
base for the intumescent char so as to inhibit Uflue effect" to
a desired degree, may also be achieved hy erecting intermediate
baffles between otherwise aligned holes so as to produce the de-
sired tortuous flow path with an adequate support base for generated
char. Such a structure is illustrated in Figure 8, wherein an
upper plate 100 with holes 106 and a lower plate 102 with holes
104 have a baffle 108 positioned between the otherwise aligned
holes 104,106. As a result, this flow path (A) is rendered tor-
tuous, whereby intumescent material positioned atop the baffle
108 will be adequately supported structurally to effec~ blocking
of the hole 106 and cessation of convective flow along path ~A)
upon actuation. Thus, it will be clear that as used in this
specification and the accompanying claims, the term "non-aligned
holes", or its equivalent, should be taken to mean, in effect,
holes between which flow is effected along a path such that the
convectively egress hole substantially entirely faces an intumes-
cent material bearing surface, such that upon actuation, the re-
sulting intumescent char is provided with an adequate structural
foundation to block the hole or otherwise cut off the normal flow
path in the face of "~lue effect" which might otherwise tend to
~` keep it openO
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Figure 9 illustra~s a specific emb~dimen~ of ~hi~ in-
vention in which a ventilated structure designated generally ~00
comprises a perforated wall element 201 which is spaced ~rom
another wall 202 which is defined by a plurality of spaced~apart
members 203 wherein the space~ 204 between adjacent members 203
define openings which are out of alig~ment wi~h openings 205 in
the planar element 201~ The element 201 although shown to be gen-
eral}y planar in shape may assume any of the corrugated forms
previously dis~ussed. Elemen~s 201 and the members 203 are held
in spaced-apart rela~ionship by conventional sid2 rails 206 having
a lower flange ~07 if desired.
Figure 10 îllustrates an installation application in
which a conventional aable support tray or the lik~ 10', is pro-
tected from fîre beneath by a ventilated barrier structure 300
suspended beneath it on any conventional suspensîon or hanger
means 301. The barrier 300 in such an installation may corres-
pond to any of the ~tructure~ hereîn described or their equivalents.
Although any of a number of intumescent materials may be
utilized in the practice of the present i~vention, it has been found
advantageous in connection with embodiments o the invention, par-
ticularly of the type herein described, to utilize one which is acatalyzed, epoxy coating containing particulate, intumescent salts
and an oxidative resistance additive, since the latter has the
beneficial effect of inhibiting oxidation of the int~escent
char to the point where it becomes relatively embrittled and
therefore structurally less resistant to the adverse effects of
the application of further heat and convective currents~ The
epoxy binder system used in such a coating may be a mixture of
an epoxide and a flexibilizing agent to provide a durable, tough,
weatherproof o~erall coating system. Pigmentation of the material
may be adjusted also to improve high temperature performance. It
is to be regarded as known to make such modifications oE commercial
, ''
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matexials as are necessary to achieve these ends. This descrip-
tion however, is by no means meant to be exclusionary but is de-
tailed here merely to demonstrate that any of a range of modifi-
cations may be made in accordance wi~h accepted technical practices
and still be within the contemplation of this invention.
Accordingly it is to be understood that the embodiments :~
of this invention herein disclosed, described and shown, are by
way of illustration and not of limitation, a~d that this invention
may be practiced in a wide variety of embodiments by those s~illed
in the cognizant arts without departing materially from the spirit
or scope of this invention.
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