Flange rings for the connection end-to-end of thin, double walled circular ducting includes a first generally-circularly shaped ring having an outer insertion flange for connection to the outer wall of the double-walled duct.
The first ring also includes: an exterior mating flange extending transversely from the outer insertion flange to define a first mating face; and an exterior hem that is substantially concentric to the outer flange to extend outwardly from the outer perimeter of the exterior mating flange. The flanged ring also includes: a second ring having an inner insertion flange connectable to the inner wall of the double-walled duct; the interior mating flange transverse from the interior insertion flange to define a second mating face; and an interior connection hem substantially concentric to the inner insertion flange and extending from the outer perimeter of the interior mating flange to overlap and be connected to the outer insertion flange.
Joint assemblies are well known for the connection of the ends of adjacent rectangular, circular, and oval HVAC duct sections. U.S. Pat. No. 5,129,690, to Meinig, recites prior art relating to such assemblies and discloses an apparatus forconnecting the ends of oval duct sections without disclosure of the method of making the apparatus; the patent does refer to U.S. Pat. No. 4,516,797, to Meinig, which discloses a one-piece flanged ring for connecting the ends of circular duct sections. U.S. Pat. No. 4,516,797 discloses a method for producing the flanged ring by contouring and then bending an elongated sheet-metal strip into an annular shape resulting in a flanged ring having an axial slit and claiming a method for producing a flangedring characterized as an elongated sheet metal strip which is contoured and subsequently bent into annular form.
The machine method used to produce such a flanged ring is known to include roll forming. However, roll forming is limited generally to sheet-metal less than 10 gauge with roll forming causing tearing or breaking of sheet-metal in the productionof flanged rings from thinner sheet-metal of gauge 10 or greater. Circular flanged rings, produced by roll forming, and thin-walled sheet-metal ducting generally do not have an absolutely circular cross section. The predominant means of manufacturingHVAC ducting is in the form of spiral seam tubes made up of helical wound sheet-metal strips with the strips interconnected by means of lock seams. The lock seams stand out from the outer duct face.
Objects of this invention are double wall circular and oval flanged rings from Lock Form Quality steel of gauge 10 to 20, for the connection of the ends of thin-, double-walled circular and oval sheet-metal tubes or ducting and how to make themby spinning, forming, and trimming, with standard machine tools and machining processes. The present invention is capable of making Flanged Rings that comply to the T24 flange profile and other profiles of the Sheet Metal and Air-ConditioningContractors National Association (SMACNA). The method includes LFQ steel strips that may be rolled into flanged ring band stock strips having strip first and second ends which are butt welded together with a tungsten inert gas process with no filler. Aspinning die, which is balanced and which has structural means or supporting structural member means, receives the flanged ring band stock which may be secured within the spinning die by appropriate means, for example by clamp means. The spinning die isrotated by means, for example by a lathe, and machine tools are employed to stretch, form and trim the flanged ring band stock to produce a first circular flanged ring. A second circular flanged ring may be produced by the same method in a secondspinning die and then attached to the first circular flanged ring to form one double-wall circular or oval flanged ring for the connection of circular and oval thin gauged double-wall pipe or ducting sections.
One preferred embodiment of the flanged ring profile described herein constitutes the Sheet Metal and Air-Conditioning Contractors National Association (SMACNA) standard T24 Flange Profile. The profile disclosed is not limited to the SMACNA T24profile. However, the method disclosed produces circular or oval flanged rings while the SMACNA T24 Flange Profile refers solely to flanges for the connection of rectangular ducting sections. This disclosure is the only known method of producing theSMACNA T24 Flange Profile for circular and oval flanged rings from 10 or greater gauge LFQ steel. The SMACNA T24 Flange Profile or cross section produced by the method described has an outer insertion flange portion which is secured within the spinningdie by means including clamp means, an exterior mating flange portion which is stretched and formed and which meets and matches an opposing mating flange portion, an exterior hem portion which is formed, and a return flange, and an inner insertion flangeportion which is secured within the second spinning die by means including clamp means, an interior mating flange portion which is stretched and formed and which meets and matches an opposing mating flange portion, and an interior hem portion which isformed.
The oval double-wall flanged ring is produced by cutting a circular, double-wall flanged ring along a diameter to produce approximately equal sized semi-circular flange ring portions. Equal length SMACNA T24 Linear Segments of the SMACNA T24Flange Profile are produced, for instance by roll forming, and are welded to the semi-circular flanged ring portions to produce the oval flanged ring.
One preferred embodiment of the present disclosed method results in the production of the SMACNA T24 Flange Profile from 10 to 20 gauge Lock Form Quality steel (under 30,000 psi yield/tensile, galvanized G60; however, any metal which can beturned in the following described process and which can be welded may be used for production). The preferred embodiment of the described method requires the preparation of flanged ring band stock from 3.87511 wide 10 to 20 gauge LFQ steel. The materialand material width may be varied as preferred.
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