Pipes and tubular conduits – Combined – With end structure
Reexamination Certificate
2001-01-24
2002-07-02
Hook, James (Department: 3752)
Pipes and tubular conduits
Combined
With end structure
C138S155000, C138SDIG004, C285S363000, C285S424000
Reexamination Certificate
active
06412519
ABSTRACT:
FIELD OF INVENTION
This invention relates to an improved system for connecting the ends of four sided rectangular sheet metal ducts wherein each duct end is provided with a double walled integral transverse flange.
BACKGROUND OF THE INVENTION
This invention relates to an improved means for connecting the ends of a pair of sheet metal duct sections. The invention particularly involves an assembly of the type including frame members defining double walled integral transverse flanges located at a duct end with adjacent frame members joined to each other by angular corner connectors.
The prior art, particularly Heilman et al U.S. Pat. No. 4,466,641 and Fischer et al U.S. Pat. No. 4,579,375, the disclosures of which are incorporated herein by reference, disclose duct connecting systems using integral transverse flanges . These arrangements include a first portion extending perpendicularly outwardly from the duct wall and a second portion bent rearwardly from the outer end of the first portion thereby forming opposing channels. The side edges of an arm of a corner connector are adapted to be snapped and crimped into place in these channels for secure assembly. To hold the adjacent duct sections together, the adjacent sections are bolted to each other at their four corner connectors, thereby forming an assembled section of duct.
Apparatus to manufacture the Heilman et al. invention is manufactured and sold by The Lockformer Company of Lisle, Ill. and is referred to in the industry as the TDC (“Transverse Duct Connector”) system. Apparatus to manufacture the Fischer et al duct is manufactured and sold by Engel Industries, Inc. of St. Louis, Mo. and is referred to in the industry as the TDF (“Transverse Duct Flange”) system. While both systems have provided the industry with a useful duct system, there remains a need in the industry for improvements to the systems as discussed herein.
FIG. 1
illustrates in cross section the roll-formed shape of the end
10
of one duct, and the roll-formed shape of the end
12
of an adjacent duct as disclosed in Heilman et al. The frame includes a first upturned portion
14
extending perpendicularly outwardly from the duct wall
16
and a second portion
18
bent rearwardly into position opposite an end portion of the duct wall. The distance between the rearwardly bent portion
18
and the end portion of the duct wall substantially corresponds to the width of an arm of a corner connector
20
. The side edges of each such arm of a corner connector
20
are adapted to engage the respective surfaces of the rearwardly bent second portion
18
and duct wall end portion whereby the corner connector
20
is held in position relative to the frame by a retainer means defined by the rearwardly bent second portion
18
.
The preferred embodiment of the Heilman et al invention includes a third outwardly facing return portion
22
at the outward edge of the rearwardly bent second portion
18
thereby forming a bead
24
. A first channel
26
is formed between the bead
24
and the outwardly extending upturned portion
14
, and a second channel
28
is formed in the duct wall opposite the first channel
26
. The side edges of an arm of a corner connector
20
are adapted to be snapped into place in these channels
26
,
28
for secure assembly of the corner connectors relative to a frame. It has been found however that the corner connectors will be displaced during manufacture and transport of the duct. Therefore, the duct flanges must be crimped (not shown in
FIG. 1
) over the adjacent arms of a corner connector to secure the corner connector in place within a duct flange.
Pursuant to Heilman et al, when assembling one duct with another, the respective frames and associated corner connectors
20
are brought together, and a bolt
30
or other suitable fastener is employed for achieving the desired connection. Prior to completion of this connection, a gasket
32
may be located between the respective frame portions for conventional purposes.
In order to strengthen the resultant duct joint formed by the Heilman et al invention, each of the arms of a corner connector
20
is provided with an offset ear which may be used for retaining a stiffener means, comprising a strip of spring steel or the like. Each stiffener means is held at its end beneath the offset ear and at its sides between channels
26
and
28
. Furthermore, a clip
34
may also be engaged around the adjacent frame portions to provide a smooth exposed joint and to strengthen the joint.
The Fischer et al duct flange, illustrated at
FIG. 2
, uses a modification of the Heilman et al invention and discloses a duct connecting system having an outstanding web portion
36
extending at
90
degrees from the duct wall
38
, with an outward-formed tracking ridge
40
spaced inwardly thereof and formed outwardly of the surface of the assembled duct wall
38
. At the outer extremity of the web
36
is an outer flange
42
having a turned-under rounded edge
44
, formed at an angle slightly in excess of 180 degrees and terminating in a spring margin
46
which extends back toward the web
36
and normally stands inwardly away from the outer flange
42
. “Button lock” lances are said to be provided through the rounded-back edge
44
projecting aft. The spacing between the web
36
and the tracking ridge
40
, which corresponds to the spacing from the web
36
of the somewhat bulbous rounded portion of the turned-under edge
44
, is fixed to accommodate the side edges of an arm of a corner connector. The depth between the spring margin
46
and the outer surface of the duct wall
38
between the ridge
40
and the web
36
, is such that the leg portions of a corner connector will snap into position and are said to be held by the spring margins
46
and the lanced projections, trapped by the tracking ridge
40
. However, it has also been found that corner connectors will fall out of the Fischer et al. duct flange without crimping. Accordingly, the duct flange of the Fischer et al. duct, in practice, is crimped to hold a corner connector in place.
As with the Heilman et al invention, the Fischer et al. duct can be readily joined with an adjacent duct end by means of bolts or fasteners. Furthermore, gasket material may also be located between adjacent frames without difficulty to decrease leakage.
In order to increase duct flange strength about the duct joint formed by the Fischer et al invention, optional reinforcing bars may be utilized between the arms of adjacent corner pieces. Each bar may be snapped in position behind the outwardly-formed ridge
40
and the rounded edge
44
of the outer flange
42
, and retained by the lanced projections. If desired, an elongated clip can also be positioned around the joint formed by adjacent duct flanges to support the middle portion of the integral flanges. Incorporation of the clip and reinforcing bar with adjacent duct flanges, helps to prevent bellowing and leakage caused by pressure exerted by materials flowing within the duct.
After issuance of the Heilman et al and Fischer et al patents, the corner connector was manually inserted into the duct flange and then manually crimped with a hammer or the like. This was, among other things, time consuming, hard on the worker and expensive to the sheet metal contractor. These problems were solved by the Cornermatic® machine sold by Iowa Precision Industries, Inc., Cedar Rapids, Iowa, and covered by U.S. Pat. Nos. 5,321,880 and 5,283,944 to Goodhue. These patents disclose an automated method and apparatus, respectively, for placement of corner connectors in transverse duct flanges. The Cornermatic® apparatus and method automatically insert a connector, such as described in Goodhue U.S. Pat. No. 5,342,100, in a duct flange and secure the connector within the flange by crimping the outer portion of the flange over the adjacent arms of the corner connector. The inventions of the Goodhue patents have been a commercial success in the industry.
BRIEF DESCRIPTION OF THE INVENTION
A primary object of the invention is to provide a double
Hook James
McCormick Paulding & Huber LLP
Met-Coil Systems Corporation
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