Abstract:
This invention relates to sealing HVAC ductwork along its joints in order to reduce air leakage. The ductwork can be sealed by the combination of a gasket and mechanical locking mechanism.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a divisional of application Ser. No. 12/133,482, filed Jun. 5, 2008, entitled “Sealing Mechanism for Ductwork,” now U.S. Pat. No. 7,992,904, which claims the benefit of U.S. Provisional Application No. 60/942,412, filed Jun. 6, 2007. All of these applications are incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to a connection for HVAC ductwork. This invention specifically relates to a sealing mechanism for HVAC ductwork that reduces air leakage in joints. 
     2. Description of the Related Art 
     Traditional ductwork has air leakage at the joints. There has been a need to add a gasket material to the joints so that when the ductwork is connected little leakage occurs. However to be able to add a gasketing material during the manufacturing process the gasketing material would have to have the following properties:
         1) Good adhesion to sheet metal;   2) Minimal surface tack; and   3) Short curing time.       

     There are numerous materials that have two out of the three qualities listed above but it is very difficult to find one having all three. Therefore, adding a gasketing material to the manufacturing process has been impractical. Typically in ductwork manufacturing it would take three seconds to form the longitudinal seam and then roll the sheet metal duct for shipping. As an example of how traditional gasketing materials would make the manufacturing process difficult one could look at adding a sealant that does not set up quickly. The sealant would have good adhesion to galvanized steel and little surface tack but does not set up quickly. It could take two to three hours or two to three days for the gasketing material to set up or cure. This length of time is not practical as either one would have to wait for each individual sheet to cure or you would have to have some type of stacking systems where the sheets are not touching each other. This would make volume manufacturing in a timely fashion impossible. Additionally, if the material sets up quickly but has too much surface tack it will cause problems in the shipping when the ducts are nested together. 
     U.S. Pat. No. 6,325,389 entitled a Self Sealing Duct/Fitting Connector describes the problems in the prior art with Conventional HVAC systems. It describes the air leakage at the joints with traditional ductwork. The solution in U.S. Pat. No. 6,325,389 is a special connector for the ductwork with a sealant. 
     There is need for sealing the connections between ductwork without having a special fitting that is incorporated in the connections manufactured into the duct work. 
     SUMMARY OF THE INVENTION 
     This invention provides for a round metal heating ventilation and air conditioning duct for residential or commercial use having a gasket that adheres to the sheet metal and has minimal surface tack. The round metal duct is made from sheet metal and used for the transportation of heated air, air, or cooled air from one location to another. The duct has a male end which is crimped and has a bead on one end of the round duct. The male end is to be inserted into a corresponding female end of another round duct. The duct also has a female end on an opposite end of the round duct to receive a corresponding male end of another round duct. 
     The gasket may be provided in a first state and can then be cured. The curing process can include an agent and may be complete in 20 minutes or less. Additionally, the gasket may be foamed. 
     The entire process of making the duct could take 20 minutes or less. 
     The cured gasket adheres to the duct proximate to an end of the duct. 
     This invention also provides for the use of ultraviolet light to quicken the curing of the gasketing material. The gasketing material could also be foamed. 
     The gasketing material can be located:
         1) on a leading edge of the male bead;   2) on the inside of the sheet proximate to the female end;   3) on an inside of the female bead; or   4) on an inside of a flared portion of the female end.       

     This invention also provided for a method of manufacturing round sheet metal ducts. Sheet metal is provided. A female end is formed on one end of the sheet metal. The female end is capable of receiving a male end of a different piece of ductwork. A male bead is formed on the male end of the duct. A longitudinal snap locking mechanism on corresponding longitudinal sides of the sheet metal is formed so that when the snap locking mechanism is connected a duct is created. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a single section of round ductwork showing a male end of a section of round ductwork. 
         FIG. 2  is a section view of a male end of the ductwork along section II-II. 
         FIG. 3  is an isometric view of a single section of round ductwork showing a female end of a section of round ductwork. 
         FIG. 4  is a section view of a female end of the ductwork along section IV-IV. 
         FIG. 5  is an isometric view of a single section of round ductwork showing a female end of the ductwork having a bead. 
         FIG. 6  is a section view of a female end of the ductwork having a bead along section VI-VI. 
         FIG. 7  is an isometric view of a single section of a ductwork having a flared female end. 
         FIG. 8  is a section view of a female end of the ductwork having a flared female end along section VIII-VIII. 
         FIG. 9  is a block diagram of the method for forming ductwork. 
         FIG. 10  is an exploded view in partial section of mating ducts of the present invention. 
         FIG. 11  is an exploded view in partial section of mating ducts of the present invention. 
         FIG. 11A  is a cross-sectional view of the longitudinal seam taken along line  11 A- 11 A of  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     Definitions 
     “round metal heating ventilation and air conditioning duct for residential or commercial use”—A cylindrical tube used to transport air—this includes spiral, round and oval ducts. 
     “forming a male crimped end and a female”—creating two ends used to connect ductwork together in the sheet metal. 
     “forming a longitudinal latching system on the sheet metal duct”—creating a mechanism in the sheet metal to connect ends of the duct so that it creates a round metal duct. 
     “gasket”—any type of sealing material that reduces air leakage between the joints formed in the ductwork. This would include a preformed product that has a tape on it and can be applied to the duct. Loctite nuva sil 5039 is an example of cured gasket material. 
     “cured”—process by which gasket hardens or toughens or turns into a gasket. Can be cross linking of polymer chains. 
     “first state” means any pre-cured state. Could be a liquid or other state of polymer or other material prior to reaching its final hardened or cured state as a gasket. 
     “adheres to the sheet metal”—attaching to the sheet metal. 
     “minimal surface tack”—When ducts are shipped they are nested against other ducts. The surface tack would be such that the ducts would not stick together and/or would not damage the gasket. This could be accomplished by putting a tape material on one side of the gasket. A gasket with a tape would be a gasket with minimal surface tack. Also an uncovered gasket that does not stick to other ducts would be a gasket with minimal surface tack. 
     “Ultraviolet”—(UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than soft X-rays. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet. 
     “foamed”—injecting some gas or blowing agent causing the gasket to grow creating bubbles in gasket causing the gasket to be more compressible. A gasketing material that has gas bubbles. A Nordson foam mixer could be used to foam the gasketing material. It is desirable to foam the gasket because less gasket material can be used. If it is foamed at 50% then 50% less gasket material is used. 
     “sealed joint” means a ductwork joint that has less leakage than a ductwork joint without a gasket. 
     “ductwork”—includes other straight pieces of duct and all types of fittings. 
     “round metal duct”—a cylindrical tube used to transport air. 
     “male end”—designed with a projecting part for fitting into a corresponding female part. 
     “female end”—designed to be hollow or have a groove into which a corresponding male part fits. 
     “a bead”—an impression formed into sheet metal. 
     “a longitudinal snap locking mechanism”—something that allows two ends of duct to be joined together without a separate fastener. Examples of this are button lock and a reeves lock. 
     “sheet metal duct”—Any type of duct work. 
     “applying an agent”—Using an agent as to aid in the curing. It could be ultraviolet light, radiation, moisture, catalyst or light or anything to help in the curing. 
     “a female transverse positioning lock”—portion of transverse positioning lock on the female end. 
     “a male transverse positioning lock”—portion of a transverse positioning lock on the male end. 
     “transverse positioning lock”—any type of mechanical structure that allows two pieces of ductwork to be rigidly joined together or locked together. 
       2 —circular duct 
       4 —crimped end 
       6 —male bead 
       8 —female end 
       10 —gasket 
       12 —leading edge 
       14 —female bead 
       16 —inside of female bead 
       18 —flared portion 
     DESCRIPTION 
       FIG. 1  shows a circular duct  2 . Male crimped end  4  has a male bead  6 . The male crimped end  4  is designed to be inserted into female end  8  of another duct. 
       FIG. 2  shows section II-II of  FIG. 1 . Fast curing gasket  10  is on a leading edge  12  of the male bead  6 . The fast curing gasket  10  is proximate to the male end  4 . 
       FIG. 3  shows a second embodiment of a circular duct  2 . The fast curing gasket  10  is proximate to the female end  8 . 
       FIG. 3  shows section IV-IV of  FIG. 3 . Fast curing gasket  10  is proximate to female end  8 . 
       FIG. 5  shows a third embodiment of a circular duct  2 . The female end  8  has a female bead  14 . 
       FIG. 6  shows section VI-VI of  FIG. 5 . Fast curing gasket  10  is located on an inside of the female bead  16 . 
       FIG. 7  shows a fourth embodiment of a circular duct  2 . Female end  8  has a flared portion  18 . 
       FIG. 8  is a cross section along VIII-VIII of  FIG. 7 . Fast curing gasket  10  is located in the flair portion  18 . When a male crimped end  4  is inserted into the female end  8 , the male crimped end  4  is able to enter without touching the gasket  10  and the gasket  10  seals on a non crimped part of the crimped male end  4 . 
       FIG. 9  is a block diagram of the method of making the circular duct. Sheet metal is cut off of a master coil and travels down a conveyor. The sheet travels into a machine where it may or may not get clipped. The optional female bead can be put in the female portion or the flared portion could be created. Optionally at the same time the gasket may be put onto the sheet at that time. Paper or some sort of covering agent might be placed onto the gasket so that it doesn&#39;t stick to adjacent pieces of ducts during shipping thereby making it have little surface tack. By doing it this way it gives the fast curing gasket time to cure and if release paper is used it is a nice flat non stick surface at this point. The gasket may travel under ultraviolet lights to cure. Additionally other agents may be used to increase curing time or aid in curing of the gasket. 
     The sheet will then travel down the conveyor to the roll forming machines where the longitudinal snap locking mechanism is formed and optionally sealant is applied. This can be seen in application Ser. No. 11/739,238 which is hereby incorporated by reference in its entirety. 
     After the longitudinal snap locking mechanism is formed the male portion is formed by crimping an end of the sheet metal. At this same time the male bead is put on. 
     At this time applicants believe that the preferred embodiment would add the gasket after the longitudinal snap locking mechanism but prior to male portion being formed. The gasket material is Loctite Nuva Sil 5039 and preferably is foamed when used in this application. It is foamed by a Nordsen Ultra Foam Machine. The foaming helps with the compressibility of the gasket. The compressibility could be determined in a manner of hardness. The hardness could be measured by a durometer and have a hardness less than Shore A 75. Preferably it would have hardness of Shore 00 in the range of 30-50. 
     A section on the end of the sheet metal may be notched out so that the longitudinal snap locking mechanism stops short of the bead so that it is not crushed when the longitudinal snap locking mechanism is formed. The notched out part helps to form a better seal because the male portion can fit better into the female portion. 
     The male and female sections can be put together and a sealed connection is created without having to take any further steps. When discussing a sealed connection it is meant to refer where minimal air leakage is present or less leakage than when there is no sealant in the connection. 
       FIG. 10  shows a first embodiment of a transverse positioning lock. On the female end  8  of a duct there can be a button lock  20  which in this embodiment is the female transverse positioning lock. The gasket  10  is on an inside of the female end  8  of the duct. The crimped male end  4  has a second bead  22  which in this embodiment is the male transverse positioning lock. The crimped male end  4  fits into the female end so that the second bead  22  slides over buttons lock  20  and locks the pipes together and ensures that the gasket lines up correctly. 
       FIG. 11  shows a second embodiment of a transverse positioning lock. The female end  8  of the duct has a female bead  14 . The female end has a cut out  24  on the longitudinal seam. The combination of the female bead  14  and the cut out  24  in this embodiment is the female transverse positioning lock. The longitudinal snap locking mechanism can be seen in  FIG. 11 . A female part  26  of the longitudinal snap locking mechanism is removed up until the female bead  14  to create the cut out  24 . The crimped male end  4  has a second bead  22  which in this embodiment is the male transverse positioning lock. The crimped male end  4  fits into the female end so that the second bead  22  slides into female bead  14  and locks the pipes together and ensures that the gasket lines up correctly and creates a proper seal. The cut out  24  allows the duct to radially expand or contract. 
     Various changes could be made in the above construction and method without departing from the scope of the invention as defined in the claims below. It is intended that all matter contained in the paragraphs above, as shown in the accompanying drawings, shall be interpreted as illustrative and not as a limitation.