Note: Descriptions are shown in the official language in which they were submitted.
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For several years it has been common practice to form air dis-
tribution ducts from panels of self-supporting rigid thermal insulation of the
mineral fiber type. These panels may be formed by, for example, a four by
eight foot sheet of insulating material to one surface of which is ~dhered a
kraft paper layer onAwhich has been deposited a thin layer of aluminum. The
.
; metal foil outer surface thus provided may be reinforced by an imbedded net-
ting of cords or l~skrim~. Heretofore these panels of duct wall have been
grooved longitudinally at the job site and the duct section formed by folding
the panel into a tube with the longitudinal seam being established and sealed
by adhesive, preferably metallic tape ~unning the length of the duct section.
In such application the tape eventually dries out and peels from the duct wall
and maintaining a sealed seam in the duct is difficult.
According to the present invention there is provided a duct board
assembly from which a thermally insulated fluid duct section may be fabricated
i comprising: a panel of self-supporting relatively rigid f~berized thermal
- insulation, metal strips applied to one face of the panel along the panel
margins and secured to the panel to provide a rigidifying frame therefor,
locking means formed at the outer margins of each of the strips mutually
cooperating to provide a closed longitudinal joint for the duct section and
to permit end-to-end attachment of successive duct sections.
.
The concept of the present invention inv~lves modifying convention-
al duct board panels by adding to it metal framing strips, on which suitable
locking or joining configurations have been preformed. By proper scoring
or grooving of the modified sheets they may be conveniently formed into the
desired duct work configuration at the installation site but may be transport-
ed to the site in flat, unformed condition. The metal framing strips applied
to the panels add to its rigidity and strength in transport and after as-
sembly. The longitudinal locking seam, made possible by the presence of the
adjacent metal framing strips when the panel has been formed into a duct
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section, makes the use of sealing tape unnecessary along the longitudinal
seam and at the junction between duct sections. Labor saving in the instal-
lation of the duct wall board of the present invention over conventional as-
sembly methods is substantial. While described herein with respect to form-
ing of rectangular duct sections it will be understood that the panels of the
present invention might also be used to form various air distribution fittings
such as
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~- duct angles, elbows, reducers and the like.
Fig. 1 is a front view of a duct wall panel embodying the present
invention.
Fig. 2 is a fragmentary, enlarged sectional view taken generally
~ along the line 2-2 of Fig. 1.
- Fig. 3 is an enlarged sectional view taken generally along the
line 3-3 of Fig. 1.
Fig. 4 is an enlarged sectional view illustrating the longitudinal
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grooves formed in the insulating board component of the panel.
Fig. 5 is a perspective, fragmentary view of a rectangular duct
.~ formed from the panel of Fig. 3.
Fig. 6 is a fragmentary sectional view illustrating the locking
means which may be used to secure adjacent duct sections together.
Fig. 7 is a fragmentary, top plan view of the locking strip shown
in Fig. 6.
Fig. 8 is an enlarged sectional view taken generally along the
line 8-8 of Fig. 5 and illustrating the locking means forming the
longitudinal seam on the duct.
Referring initially to Fig. 1, the duct wall assembly of the
20 present invention is composed of a central panel 10 of rigid, self-
supporting thermal insulation which is made of a mineral fiber type.
; The insulation is covered on one surface by a layer of kraft paper which
is a &ered to the insulation. The paper has a thin metal foil covering
lOa and a network of reinforcing cords or "skrim" may be provided in
the paper. These sheets of foil surfaced insulation are well known in
, the art and commercially available in variously sized panels.
Secured to the outer marginal portions of the duct wall are metal
framing members, the framing members for the longitudinal edges of the
sheet being indicated at 11 and 12 and the framing members for the
30 transverse margins of the sheet being indicated at 13 and 14. The
metal framing members may be formed of galvanized metal and prior to
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~ their attachment to the foil covered surface of the insulating
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material 10, the metal strips forming the framing members are provided
~`~ with locking means. As may be seen in Fig. 2 the strip 11 is bent
` upon itself to form a slip lock configuration with a bight area lla
~; and a inwardly extending locking tab llb. The strips 11, 12, 13 and
14 are attached to the insulation board by means of conventional
fasteners 18, carrying enlarged heads 18a. The fasteners extend through
. the insulation material and its overlying foil covering and the tip of
;
the fastener is secured to the overlying strip by any suitable means
such as spot-welding as indicated at 18b in Fig. 2. It will be
understood that the locking configuration formed on the outer margin of
the strips is completed prior to securing the strips to the insulation
board.
As may be seen in Fig. 3, the longitudinal metal strip 12 is bent
inwardly along its outer margin to form the extending flange 12a and,
, spaced along the flange, there are provided protrusions 12b which extend
from the surface of the flange. As shown in Fig. 4, the insulation
board may be grooved or scored as indicated at 19 along longitudinal
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, lines paralleling the longitudinal margins of the sheet. This groovingi 20 is indicated by broken lines in Fig. 1. The longitudinal grooves define
~: the width of the duct walls and establish the lines along which the
sheet is to be bent in forming the rectangular duct of Fig. 5 as will
subsequently be explained.
'- The transverse metal strips 13 and 14 are each provided with
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locking means which takes the form of an outward, turned-back flange
13a and 14a respectively, the flange being visible in both Fig. 1 and
Fig. 6. A rectangular duct section is formed from the panel of Fig. 1
by bending the panel along the lines 19 at 90 bringing the longitudinal
strips 11 and 12 together as shown in Fig. 5. As the strips 11 and
3~ 12 are brought together the flange 12a on the strip 12 is inserted into
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; the bight area lla formed at the outer margin of the strip 11. When
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^~ the flange 12a is inserted to the proper depth the locking tab llb
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will snap behind the spaced protrusions 12b carried by the flange 12a
as shown in Fig. 8. The adjoining margins of the metal members 11
and 12 will then be securely locked together and the slight compression
of the insulating material underlying the strips 11 and 12 will provide
a sealed, secured joint which requires no additional taping.
The duct section shown in Fig. 5, formed from the panel of Fig. 1,
may be joined to similar duct sections, end-to-end, as shown in Fig. 6.
The return bends 13a on the transverse framing strips 13 of two sections
receive a drive cleat 21 as shown in Fig. 6, the cleat being shown
fragmentarily also in Fig. 7. The cleat is formed by turning inwardly
two marginal areas 21a, these turned-back portions being received in
the bight of the portions 13a. A flat tab 21b is formed at each end
of the cleat and this may be bent inwardly to lock the cleat in place
overlying the junction of the two adjacent duct sections. The use of
a drive cleat, as illustrated, serves to draw the abutting margins of
the insulating material tightly together thereby obviating the use of
sealing tape, however, it will be understood that other forms of
locking means might be utilized to secure together adjacent duct
sections.
While the invention has been disclosed and described in some
detail in the drawings and foregoing description, they are to be
considered as illustrative and not restrictive in character, as other
modifications within the scope of the invention may readily suggest
themselves to persons skilled in the art.
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