Field Of Invention

This invention relates to coupling rings for receiving and joining circular air ducts.

Related Applications

This application is a continuation-in-part of copending application Serial No. 07/776,592, filed October 11, 1991, and incorporates by reference the disclosure of copending U.S. Application Serial No. 07/907,872, filed July 2, 1992, Attorney Docket No. KEH 0104 PUS.

Background Of The Invention

Over the years, many suggestions have been made for joining circular air ducts. The following U.S. Patents suggest various couplings for circular or rectangular pipe:

180,416 3,689,114

1,921,642 4,447,078

1,762,766 4,558,892

1,811,277 4,669,762

3,415,543 4,941,693

Despite these coupling designs, the principal way in which circular ducts have been connected over the years is the use of the so-called double S-lock. Such is simply a strip of sheet metal that has been folded upon itself to provide oppositely opening grooves and then bent into circular configuration with the ends aligned and joined in any suitable fashion. Such double

S-lock locks have been used for both circular and rectangular ducts. After they are installed, drive screws are inserted every 3" or so around the duct and then the joint is wrapped and painted to effect an air¬ tight seal. While the double S locking joint is in itself inexpensive, the time required by the duct installer raises the cost per joint considerably. Effecting airtight joints in circular duct work has been quite labor intensive.

In Patent 4,941,693, a connector is disclosed which is formed of two cylindrical shapes that must be deformed and thereafter nested and riveted together. The cost of manufacture of this coupling makes it expensive to use. In addition, because of the relative¬ ly long axial depth of the oppositely opening grooves in relation to their radial width, when sealant is placed in the grooves and it is then attempted to insert the ends of the ducts, a hydraulic lock tends to develop making it difficult to obtain satisfactory insertion of the duct ends in the grooves. Additionally, as the ducts are slid over the projecting flanges of the cou¬ pling, the sealant tends to be wiped off the flanges thereby destroying the seal between the duct and the coupling at such flanges. Clow 180,416 is similar to the structure of U.S. Patent 4,941,693 and presents many of the same problems in its use.

Patent 4,669,762 if somehow usable for circu¬ lar duct work would create a hydraulic lock between the sealant, the duct and the coupling as the duct is inserted in the coupling.

My own prior patent 3,415,543 was never adapted for use with circular ducts and the relatively

large channel section could not be bent into circular configuration.

Summary Of The Invention

I have disclosed a coupling ring for circular, oval or flat/oval ducts which may be manufactured at a low cost and installed quickly and easily by the duct installer. The coupling is formed of a single strip of sheet metal such as 22 gauge which is formed in the flat to exhibit an elongated rib disposed medially of the strip and providing oppositely opening duct receiving grooves. This strip is then hooped, i.e., bent into circular configuration, while simultaneously crimping the flanges to prevent distortion of the duct receiving grooves, and the ends are then brought into alignment and secured together as by welding to a butt block. Sealant is placed in the grooves prior to insertion of the ducts. Preferably the radial width of the grooves is between four and six times the wall thickness of the ducts and the axial length of each groove may be sub¬ stantially equal to the width of the groove or not more than about 10% to 15% greater than the width. This avoids any hydraulic lock when the ducts and sealing rings are assembled. Fasteners may be driven through the ducts and flanges of the ring to lock them together. In order to connect ducts to conventional fittings having a male end of larger diameter than the ducts, I have modified the coupling ring to have one of its grooves made larger than the other to be telescoped over the male end of the fitting. Fasteners are then driven through the duct and into the fitting to secure the joint. In manufacturing a coupling ring of this configuration, the flat strip, which is formed as above stated, has one side of the medial rib of a greater

height than the other whereby the oppositely opening duct receiving grooves are offset from each other by the difference in radius of the end of the fitting and the duct to be joined. This strip is then bent into circular configuration and the ends joined as by welding. This then provides oppositely opening radially offset grooves, one of a diameter to receive the end of the duct and the other a larger diameter to receive the larger diameter end of the fitting.

Brief Description Of The Drawings

FIGURE 1 is a schematic view of a portion of a duct system showing the utilization of my improved sealing ring?

FIGURE 2 is a cross-sectional view taken along line 2-2 of Figure 1;

FIGURE 3 is a front elevation of a coupling ring embodying my invention;

FIGURE 4 is a cross-sectional view taken along line 4-4 of Figure 3; ,

FIGURE 5 is an enlarged fragmentary cross- sectional view through one of the duct receiving grooves;

FIGURE 6 is a view similar to Figure 2 but showing a modification of the invention;

FIGURE 7 is a fragmentary cross-sectional view similar to Figure 2 but showing a stripable cover for protecting the sealant;

FIGURE 8 is a side elevation of a sheet metal strip which has been formed in the flat and prior to hooping;

FIGURE 9 is a schematic view of a set of hooping rollers for bending the flat strip of Figure 8 into circular configuration and crimping the flanges;

FIGURE 10 is a side elevation of an elbow fitting for circular duct work to which ducts are connected utilizing a modified form of my duct coupling; and

FIGURE 11 is a cross-sectional view taken on the line 11-11 of Figure 10.

Description Of Preferred Embodiments

As shown in Figures 2 and 3, my improved sealing ring 10 is formed of a single strip of sheet metal shaped to provide oppositely extending cylindrical flanges 34 and 36 and a channel-shaped annular rib 11 encircling the flanges at their proximal ends and connecting them together. Axially outwardly opening grooves 20 and 22 at opposite sides of the rib 11 at the connection between the rib and the flanges are intended to receive the ends of the ducts 30 and 31 into which the flanges 34 and 36 are telescoped. Each flange is circumferentially crimped at 36 and 38 between the grooves 20 and 22 and the distal ends 46 and 47 of the flanges.

More specifically, the single strip of sheet metal is shaped to provide the annular rib 11 with an outer wall 12, opposed lateral edge walls 14 and 16 and

an inner wall 18. The inner wall is bent upon itself to exhibit a pair of oppositely opening, annular, relative¬ ly shallow duct receiving grooves 20 and 22 heretofore mentioned. The grooves have radial outer wall portions 24 and 26 which overly the outside 28 and 29 of the duct elements 30 and 31 at the end edge 32 and 33. Inner cylindrical flanges 34 and 36 are intended to be re¬ ceived within the duct elements 30 and 31 and extend axially substantially beyond the rib 11. The flanges 34 and 36 are characterized by circumferential crimping 36 and 38 heretofore mentioned which extends completely around the ring having a succession of ridges 40 and grooves 42 which extend axially of the flanges from the outer end 44 spaced inwardly from the distal end 46 of the flange or end 47 of the other flange) to an inner end 48 spaced slightly outwardly of the groove 20 and groove 22. From the outer end or edge of the crimping to the end of the flange, it is bent angularly inwardly as at 50 and 52 to form guiding ramp portions facilitat¬ ing introduction of the flange into the ducts.

Thus, it will be noted that the inner wall 18 of the channel-shaped annular rib 11 comprises the pair of wall portions 24 and 26 which extend axially and radially inwardly from the lateral edge walls 14 and 16 toward each other and into abutment at 54 where they are reversely bent upon themselves to form the bottom 56 and 58 of the grooves 20 and 22. This reverse bend at the bottom walls 56 and 58 is somewhat teardrop-shaped at 60 and 62 forming a pocket at 64 and 66 to help retain in the grooves a sealant 68 and 70 which is placed in each groove prior to assembly of the coupling ring with the ducts, and preferably at the time of manufacture of the coupling ring as hereinafter mentioned. It is to be noted that between the inner ends of the crimps and the

bottoms 56 and 58 of the grooves, the flange is smooth as at 59 within the pocket, thus facilitating the sealing between the opposed surfaces of the coupling ring and ducts.

In use, the duct elements 30 and 31 are telescoped over the flanges 34 and 36 and the edges 32 and 33 are forced into the sealant which is extruded back along the duct to form a visible bead along the outside 28 of the duct as shown in Figure 2. The installer will be able to tell whether the duct has properly seated on the flange and whether a seal will be effected by observing whether the sealant has been extruded partially between the annular rib 11 and the outer surface of the duct completely around the duct. The duct may extend to the bottom walls 56 and 58 or may be spaced therefrom as shown in Figure 2. In either event, when the duct has properly entered the grooves, there will be evidence of extrusion of the sealant between the rib and the duct and such extrusion should be substantially uniform all around the duct indicating a proper penetration of the duct within the sealant.

The ducts are retained in place on the ring by fasteners, one of which is shown at 74. The fasteners may be sheet metal drive screws of conventional con¬ struction. Three such fasteners driven equally spaced around each duct and into each flange should be suffi¬ cient for most installations. My coupling ring may be used for joining the ends of duct elements such as a "Y" 30 and straight ducts 31, 56 and 78 or simply a pair of straight duct sections as at 76 and 78 in Figure 1. The width, or radial dimension 5D of the grooves 20 and 22 is about between four to six times, and preferably, five times the nominal wall thickness D of the typical duct

section 30 to be joined by my sealing ring. In addi¬ tion, the axial length L of the groove as shown in Figure 5 is the same as or only slightly greater than the width W. In one embodiment, the length was only 10% greater than the width, and this proved quite satisfac¬ tory, though I believe the length could probably be up to as much as 15% greater than the width W. By provid¬ ing these dimensional relationships, the duct elements may be easily assembled to the coupling ring without a hydraulic lock developing in the sealant between the coupling ring and the duct as occurs in the prior art and without wiping the sealant off the flange as would occur in a joint such as shown in U.S. Patent 4,941,693.

Also, the pockets 64 and 66 in each groove will retain a quantity of the sealant to provide a continuous bead around the duct. These pockets 64 and 66 are formed at the time the strip is bent into its hoop shape and are displaced inwardly of the ring by the dimension A shown in Figure 5 below the cylindrical surface 80 of the flange. Thus, sealant in such pockets will not be wiped therefrom by a duct end wiping over the surface 80 as it slides toward the bottom of the groove.

To manufacture the coupling ring, a strip of sheet metal of 22 gauge (0.036 inches) LFQ, G-90 steel having straight parallel lateral edges 46 and 47 is fed lengthwise into a rolling mill (not shown) having sets of rolls which will form the channel-shaped rib ll ¹ (the designation given such rib prior to hooping the strip) , grooves 20 and 22, and the coplanar flanges, all in a flat strip as shown in Figure 8 and in Figure 5. I Figure 5, the groove as rolled in the flat strip is shown in phantom outline curve 63. This strip is then

hooped or bent into a hoop or annular shape with the rib ll ¹ on the outside by feeding the strip through a second set of rolls 100, 102 and 104, and such additional rolls as necessary, as schematically shown in Figure 9. At the time the strip is bent into its circular shape, the crimps or flutes 36 and 38 are formed in the flanges 46 and 47. This may be accomplished by having cooperating lands and grooves in the rolls 100, 102 and 104 and as the strip is passed between them and bent, the crimps are simultaneously formed. A preferred embodiment of the method and apparatus for effecting the hooping of the strip is disclosed in said co-pending application Serial No. 907,872, filed July 2, 1992, Attorney Docket No. KEH 0104 PUS. The number and depth of the crimps or flutes must be selected to prevent unwanted distortion of the grooves 20 and 22 during the hooping operation. This, in turn, will depend on the diameter of the ring to be formed, the gauge of metal being used, etc. At the time of hooping, the pockets 64 and 66 are formed in the grooves as a natural result of the bending of the strip.

Following hooping, the free ends of the strip are aligned as at 106 and a butt block 108 (Figs. 3 and 4) may be spot welded over the meeting ends on the inside of the ring. I have also shown in Figure 4 some of the angles that have proven satisfactory for the ramp portion 52 and the outer wall 24 of the rib.

In Figure 6, I have shown a modification wherein a reinforcing annular flange 110 is disposed medially on outer wall 12 of the rib 11 and welded thereto. The flange may also be used advantageously to hang the coupling ring for supporting the duct, and for this purpose, a hanger 112 may be pinned or otherwise

secured thereto with a tail 114 for attachment to the ceiling structure of the building in which the duct is to be installed.

In a preferred embodiment, after manufacture of the coupling ring has been completed, the oppositely opening grooves 20 and 22 may have the sealant 68 and 70 deposited therein as shown in Figure 7. To prevent this sealant from being contaminated or inadvertently dis¬ placed, a stripable cover 116 may be wrapped around the coupling ring over the rib and the grooves and about the flanges. This cover may be simply a thin, clinging-type plastic film or an adhesive coated fabric or plastic strip. The stripable cover will then be removed by the duct installer at the time the coupling is used.

Because of the construction of the annular rib 11, this coupling ring will allow the ducts to move slightly through a bending of the top wall 11 and the lateral edge walls 14 and 16 without destroying the seal between the duct elements and the grooves 20 and 22. Thus, if the duct is installed in a building subjected to seismic disturbances, the sealing ring should provide a continuing seal.

I have found that it is not necessary to trap a relatively long length of the duct in a coupling to effect a good seal and reliable joint. I avoid this by providing sealant between the coupling ring and both the inside and outside of the duct, and trapping the ends 32 and 33 against expansion by the overlying annular rib 11. Thus internal air pressure cannot cause the end of the duct to expand radially and break the seal.

My construction also allows a greater toler¬ ance variation in duct diameter than does the prior art. In my design up to 1/8" variation in duct diameter can be accommodated which in a design such as that in U.S. Patent No. 4,941,693 will required quite precise match¬ ing of the duct and the coupling.

My construction, because of the "I-beam" shape of the annular rib 11, is quite strong and resistant to collapse or buckle.

In Figure 10 I have shown a conventional elbow fitting 120 having opposite end portions 122 and 124 with annular beads 126 and 128 spaced from the distal ends. These end portions are conventionally of slightly larger diameter than the ducts to be connected to them. Conventional connectors have heretofore been employed for connecting the ends of ducts to these male end portions 122 and 124. In Figure 11 I have shown a modified connector embodying my invention which is similar to the connectors hereinbefore disclosed except that the oppositely opening grooves 20' and 22' are different diameters. Groove 20' is of a diameter to receive the end of the duct D while groove 22' is of larger diameter to receive the male end portion 124 of the elbow fitting. Fasteners 74' extend through the telescoped duct and elbow to hold them together. Sealant may also be provided as shown and hereinbefore described. Because of the speed with which the connection can be effected using any improved coupling ring, ducts may be connected to fittings such as elbows and the like and a good seal obtained much more quickly than with prior art connectors.

To manufacture the coupling ring of Figure 9, a flat strip of sheet metal as before described is first rolled to provide a central rib similar to rib 11' in Figure 8*but one side wall 16' of the rib (see Figure 11) is of greater vertical dimension than the opposite wall 14' . The difference in the vertical heights of these walls is substantially equal to the difference in the radii between the duct D and the end of the fitting to which the duct is to be coupled. The flanges 34' and 36' are similarly offset by this difference in the radii of the Duct D and the end of the fitting. Thus, when the strip is hooped as shown in Figure 11, the dissimilar diameters of the duct D and the fitting end 124 are readily accommodated.

While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.