Elongated member for joining ducts

An apparatus for joining flanged, abutting duct ends or for reinforcing ducts comprises an elongated coupling member including a V-shaped portion made up of two slanting walls approaching an apex and having lower portions spaced apart a given distance. It also includes inwardly turned edges on the slanting walls spaced from the apex, extensions of the slanting walls diverging from one another as the slanting walls approach the apex extending from the slanting walls a distance about equal to the given distance, and a joining portion extending from the extensions doubling back over the apex. The extensions and the joining portions have substantial parallel segments with a curved connection between the parallel segments. The edges, slanting walls, extensions and joining portion being integrally formed of sheet metal. The inwardly turned edges may be urged onto straddling relationship with flanged duct ends to hold the ends together and the V-shaped portion, extensions and joining portion provide a strong, reinforced duct joint. Or the coupling member may be affixed to a sidewall of a duct to reinforce the duct.

BACKGROUND OF THE INVENTION 
The present invention relates to improvements in coupling members for 
connecting flanged duct ends. 
In particular, it relates to an improvement in the duct connector disclosed 
in U.S. Pat. No. 4,461,499 to Hunter et al entitled "Transverse Joint 
System for sheet Metal Ducts", the entire disclosure of which is 
incorporated herein by reference. That patent is assigned to the assignee 
of the present application, and it depicts a system for connecting sheet 
metal duct sections. That system has proven to be very useful over the 
years. It includes flanging the ends of sheet metal ducts, abutting them 
at an interface and forming a plurality of spaced tabs in the wall surface 
of the flanges, which tabs protrude outwardly in a direction away from the 
interface. A generally V-shaped coupling member having sidewalls with free 
edges folded back under the corresponding side wall is then assembled over 
a pair of abutted flanges, with the edges of the folded under portions 
snapping in behind the tabs to lock the flanges together. Such V-shaped 
coupling members are arrayed around the periphery of the duct and, at 
their intersection, are interleaved. The coupling members are secured by 
drilling the interleaved portions and joining them with a nut and bolt 
arrangement. 
The present invention focuses on improving the coupling member so that when 
it couples the flanged ends of the ducts together, the joint has a greater 
strength than the coupling member of the aforementioned patent. The 
coupling member of the present invention may also be used as a 
reinforcement of a duct side wall, spaced from the joint, as disclosed in 
my copending application entitled "Duct Reinforcement", Ser. No. 819,405, 
filed Jan. 10, 1992. The invention may also be configured to be used in 
conjunction with corner pieces as described in my copending application 
entitled "Corner Pieces for Improved Duct Connector", Ser. No. 818,848 
filed Jan. 10, 1992 herewith. The disclosures of the two aforementioned 
applications are incorporated herein by reference. 
The strength of the joint provided by the coupling member as described in 
my prior patent is adequate for most circumstances, however, when very 
large cross section ducts are to be joined, additional reinforcement is 
desirable to prevent sagging, bowing and bulging caused by high inner 
pressures. While other reinforcement means are known, including applying 
angle irons to the outside of the ducts, the installation of those angle 
irons in addition to the installation of the coupling member adds labor 
and parts expense. Thus, it would be advantageous if these expenses could 
be avoided. 
SUMMARY OF THE INVENTION 
The present invention fulfills this need in the art by providing an 
apparatus for joining flanged, abutting duct ends or for reinforcing 
ducts. The apparatus includes an elongated coupling member including a 
V-shaped portion made up of two slanting walls approaching an apex. 
Inwardly turned edges on the slanting walls are spaced from the apex, and 
extensions of the slanting walls diverge from one another as the slanting 
walls approach the apex. A joining portion extends from the extensions, 
doubling back over the apex. The inwardly turned edges may be urged onto 
straddling relationship with flanged duct ends to hold the ends together 
and the V-shaped portion, extensions and joining portion provide a strong, 
reinforced duct joint. Or, the coupling member may be affixed to a 
sidewall of a duct at a location other than at a joint to reinforce the 
duct. 
Typically, the edges, slanting walls, extensions and joining portion are 
integrally formed of sheet metal. Preferably the slanting walls have lower 
portions spaced apart a given distance and the extensions extend from the 
slanting walls a distance about equal to the given distance. 
In a preferred embodiment the extensions and the joining portions have 
substantial parallel segments, and the extensions and the joining portions 
are integrally formed with a curved connection between them. 
In one embodiment the coupling member is about as long as the length of the 
side of the duct, and corner pieces join adjacent coupling members to 
complete circumscription of the duct. Alternatively, the coupling members 
may be long enough to intersect and be held together by interleaving 
and/or by fasteners. 
The invention also provides a duct as joined with the coupling member 
and/or reinforced with the coupling members.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As can be seen in FIG. 1, two duct sections 10A and 10B are provided with 
outwardly extending flanges 12A,14A,16A,18A,12B,14B,16B,18B. If desired, 
the flanges may be provided with tabs 20 in accordance with the invention 
as described in our prior U.S. Pat. No. 4,461,499. A coupling member 30 
includes a V-shaped portion 34 made up of two slanting sides 33,35 
approaching an apex 32. Each side terminates in an inwardly turned edge 
38,36 respectively. Spaced from the inwardly turned edges are extensions 
37,39 which diverge from the apex. The extensions 37,39 turn back on 
themselves to form a joining portion 41. As can be seen, substantial 
portions of the extensions 37,39 are parallel with the joining portion 41. 
The extra corrugations caused by turning out the extensions 37,39 and then 
turning them back on themselves provides longitudinal rigidity to the 
coupling member 30. Also, they add additional material to the coupling 
member to provide additional strength. 
In the embodiment shown in FIG. 1, the coupling member 30 is shown about as 
long as the length of the flanges 12A,12B. The coupling member 30 is 
slipped over the abutted flanges 12A,12B and pressed home until the 
inwardly turned edges 36,38 snap behind the tabs 20. Similar coupling 
members are applied to the other flange pairs 14A,14B,16A,16B,18A,18B. The 
corners of the joint may be completed by the addition of corner pieces as 
desired. Particular corner piece embodiments can include any of those set 
forth in my copending application entitled "Corner Pieces for Improved 
Duct Connector", mentioned above. 
Referring to FIG. 2, a perspective view of a duct having several units of 
the reinforcing duct coupling of the present invention installed in it 
will be of assistance in further understanding the invention. In FIG. 2, 
the coupling members 44,46,48,49 are shown mounted on a duct 51 provided 
with a bead reinforcement as discussed in my copending application 
entitled "Duct Reinforcement" mentioned above. The coupling member shown 
in FIG. 2 may, of course, also be used to join duct section as discussed 
above in connection with FIG. 1. In FIG. 2, the coupling members 44,46 are 
provided of a length of about the same as the length of the corresponding 
duct side wall. Thus, a corner piece 50 is provided to complete the corner 
where the two coupling members 44,46 meet. The coupling member 50 shown in 
FIG. 2 is a single piece coupling member. 
Coupling members 48,49 are shown somewhat longer so that they intersect and 
their sidewalls are interleaved at their intersection point. The 
intersected and interleaved coupling members 48,49 can then be drilled 
with a hole and joined with a nut and bolt 53. 
The intersection of the coupling members 46,48 is completed with a 
two-piece corner piece. That is, the corner piece has one leg 56 which 
extends into coupling member 46 and another leg 54 which extends into 
coupling member 48. The two legs 54,56 are then joined by a nut and bolt 
58. 
As will be apparent, the three corner treatments shown in FIG. 2 are 
exemplary only. Various other corner arrangements can be substituted. 
Moreover, in actual practice, in a given installation, all of the corners 
are usually treated identically, rather than the multiple modes shown here 
for illustration purposes. 
Referring now to FIG. 3, as a sectional view along lines 3--3 of FIG. 2, 
the wall of the duct 51 is provided with a bead 64, as is conventional. 
The coupling member 49 is installed so that the inwardly turned edges 
36,38 straddle the bead 64. A self-tapping screw 28 is then driven 
outwardly through the bead 64 so that its threads 43 engage the inwardly 
turned edges 36,38 to hold the coupling member 49 in place. 
The extensions 37,39 thus provide additional rigidity to the coupling 
member 49 to aid in its reinforcement of the duct 51. 
Those of ordinary skill in the art will appreciate that various 
modifications to the invention could be made and still fall within the 
scope of the invention. For example, various other deformations of the 
extensions 37,39 could be implemented, including bowing them down toward 
the edges 36,38. Or, their size could be varied or additional corrugations 
could be included. All of these are deemed to be within the scope of the 
invention.