Abstract:
An air duct section is formed from at least two longitudinal duct portions that snap together to form a hollow duct having a longitudinal direction. The duct section has a pair of ends that are adjustable between male and female configurations. The interlocking device used to connect the duct portions allows continuous adjustability between the first end and the second end of the duct section while minimizing air leaks and providing structural integrity to the duct section.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority from U.S. Provisional Application Ser. No. 60/524,146 filed Nov. 21, 2003; the disclosure of which are incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Technical Field  
         [0003]     The present invention generally relates to conduits and ducts and, more particularly, the types of conduits and ducts that are formed from multiple longitudinal pieces. Specifically, the present invention relates to a two piece air duct that is formed from two longitudinal pieces that snap together in a manner that allows the ends of the section to be adjusted between male and female configurations.  
         [0004]     2. Background Information  
         [0005]     Air ducts in residential and commercial heating, ventilation, and air conditioning (HVAC) are typically formed from relatively thin sheet metal. The ducts may have round or rectangular cross sections and are typically purchased in formed sections of various lengths. Each section has a male end and a female end so that the duct sections may be fit together to form long lengths of duct. The ends may also be used to connect the duct sections to other duct components such as duct boots, duct elbows, diffusers, headers, and the like. Once two components are frictionally held together by inserting the male end into a female end, the joint may be secured with a fastener such as a sheet metal screw. Other installers simply use duct tape to hold the joints together.  
         [0006]     As most HVAC installers know, installing sheet metal duct work is hazardous and frustrating when the installer must customize a standard-length duct section to fit a specific location on the job. The customization process typically involves cutting the sheet metal material which produces a sharp, and at times ragged, edge that can injure the fingers and hands of the installer. In addition to the sharp edges created by customizing a standard-length duct, the process of cutting a round or rectangular duct to length is somewhat difficult and time consuming. When a duct section is cut to length, one of the ends is removed leaving a new end that may not mate with the exposed end of the other component. In some situations, an adapter ring must be used to connect the two components after a duct section has been cut to length. Installers thus desire a duct that may be used in HVAC systems that may be easily and safely customized.  
         [0007]     In addition to the installation problems, existing metal duct sections must be fabricated in the field from flat sheet metal or must be shipped in large shipping containers that necessarily contain a large volume of air. Although the large volume of air is not heavy, the containers are rather large. The large containers increase the cost of shipping sheet metal ducts from manufacturers to users. The industry thus desires a duct that is more compact for shipping.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     The invention provides an air duct section that is formed from at least two longitudinal duct portions that snap together to form a hollow duct having a longitudinal direction. The duct section has a pair of ends that are adjustable between male and female configurations. The interlocking device used to connect the duct portions allows continuous adjustability between the first end and the second end of the duct section while minimizing air leaks and providing structural integrity to the duct section.  
         [0009]     In one embodiment, the air duct includes first and second duct portions that each have a longitudinal direction. Each of the first and second duct portions has a first end and a second end. Each of the first and second duct portions has a male tooth and a female tooth with each of the teeth extending continuously in the longitudinal direction of the duct portions. The male tooth of the first duct portion engages the female tooth of the second duct portion and the female tooth of the first duct portion engaging the male tooth of the second duct portion to form a duct section. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0010]      FIG. 1  is a perspective view of one of the duct portions used to form the two piece duct section of the present invention.  
         [0011]      FIG. 2  is an end view of  FIG. 1 .  
         [0012]      FIG. 3  is an enlarged view of one of the encircled portions of  FIG. 2 .  
         [0013]      FIG. 4  is an enlarged view of the other of the encircled portions of  FIG. 2 .  
         [0014]      FIG. 5  is an end view of the two piece duct section assembled from two of the duct portions shown in  FIG. 1 .  
         [0015]      FIG. 6  is an enlarged view of the encircled portion of  FIG. 5 .  
         [0016]      FIG. 7  is an elevation view showing three duct sections connected together and made in accordance with the present invention.  
         [0017]      FIG. 8  is a section view taken along line  8 - 8  of  FIG. 7 .  
         [0018]      FIG. 9  is an enlarged view of one of the encircled portions of  FIG. 8 .  
         [0019]      FIG. 9A  is an enlarged view of the other of the encircled portions of  FIG. 8 .  
         [0020]      FIG. 10  is an elevation view showing one of the duct sections of the present invention used to connect a duct elbow and a duct boot.  
         [0021]      FIG. 11  is a section view taken along line  11 - 11  of  FIG. 10 .  
         [0022]      FIG. 12  is an enlarged view of the encircled portion of  FIG. 11 .  
         [0023]      FIG. 13  is a section view taken along line  13 - 13  of  FIG. 10 .  
         [0024]      FIG. 14  is an enlarged view of the encircled portion of  FIG. 13 .  
         [0025]      FIG. 15  is an elevation view showing a duct section made in accordance with the concepts of the present invention used to connect a pair of duct elbows.  
         [0026]      FIG. 16  is an elevation view showing the duct section of the present invention used to connect a pair of duct elements.  
         [0027]      FIG. 17  is an end view of an alternative duct portion used to form the duct sections of the present invention.  
         [0028]      FIG. 18  is an end view of a duct section formed with three duct portions. 
     
    
       [0029]     Similar numbers refer to similar parts throughout the specification.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0030]     A duct section made in accordance with the concepts of the present invention is indicated generally by the numeral 10 in the accompanying drawings. Duct section  10  is formed by interlocking at least two duct portions  12  that interlock at two longitudinal joints  14  to form duct section  10 . Each longitudinal joint includes a male tooth  16  and a female tooth  18  that lock together when portions  12  are connected to form duct section  10 . Each tooth  16  and  18  defines a locking surface  20  and an angled surface  22  that allow teeth  16  and  18  to cooperate to fit together and then lock portions  12  in place. When only two portions  12  are used to form duct section  10 , locking surfaces  20  are 180° apart from each other as depicted in  FIG. 2  such that a 360° opening is formed when two duct portions  12  are connected together as shown in  FIG. 5 . When more than two duct portions  12  are used to form duct section  10  as shown in  FIG. 18 , the angle between locking surfaces  20  on a single duct portion  12  is less than 180°. For instance, when three duct portions  12  are used to form a duct section  10 , locking surfaces  20  may be 120° apart.  
         [0031]     Male tooth  16  has a length indicated by dimension line  30  in  FIG. 4 . Female tooth  18  has a length indicated by the dimension line  32  in  FIG. 3 . Female tooth  18  is disposed at the end of a jaw  34  formed by an inner jaw portion  36  and an outer jaw portion  38 . In the exemplary embodiment of the invention depicted in the drawings, female tooth  18  extends inwardly from outer jaw portion  38  while male tooth  16  extends outwardly. In other embodiments of the invention, female tooth  18  may extend outwardly from inner jaw portion  36 . In such an alternative embodiment, male tooth  16  would project inwardly instead of outwardly as depicted in  FIG. 4 . Inner and outer jaw portions  36  and  38  define a locking channel  40  that receives male tooth  16  when longitudinal joints  14  are formed. As shown in  FIG. 6 , channel  40  has a width substantially equal to the thickness of male tooth  16  such that a tight fit is formed between teeth  16  and  18 . Channel  40  has a length indicated by the dimension line  42  in  FIG. 3  that allows male tooth  16  to slide between a female position ( FIG. 6 ) and a male position ( FIG. 9 ). The length of channel  40  may be four times the length of tooth  16  as shown in the drawings. When male tooth  16  is in the female position depicted in  FIG. 6 , the inside diameter of duct section  10  is large enough to receive a male end of another HVAC component. When male tooth  16  is in the male position depicted in  FIG. 9 , the outer diameter of duct section  10  is small enough to be received inside a female end of another HVAC component. Channel  40  is free of steps and locking devices between the male and female positions of male tooth  16  so that male tooth  16  may freely slide between the female and male positions along the length of duct section  10 . Channel  40  thus allows a single duct section  10  to be configured with two male ends, two female ends, or one male end and one female end. When duct section  10  is configured with one male end and one female end, the position of male tooth  16  varies continuously with respect to channel  40  along the longitudinal length of duct section  10 .  
         [0032]      FIG. 5  shows one end of section  10  configured in the female configuration.  FIGS. 7 and 8  show adjacent sections  10  with one end configured in a male configuration and slid into the female end of the other section  10  as shown in  FIG. 8 .  FIGS. 9 and 9 A show the different configurations for the teeth.  FIGS. 10, 11 , and  12  show an end of a section configured in a female orientation and receiving the end of a duct elbow.  FIGS. 10, 13 , and  14  show the other end of section  10  configured in a male configuration and received in the female end of a duct boot.  FIG. 15  shows a duct section having two female ends used with two duct elbows.  FIG. 16  shows a duct section with two male ends used with two other HVAC components.  
         [0033]      FIG. 17  depicts an alternative version of a duct portion. The alternative version is formed in a flattened configuration (depicted in solid lines in  FIG. 17 ) such that the portion must be flexed to form a half circle as shown in the dashed in  FIG. 17 . This type of configuration builds a spring force into the duct sections that helps hold the duct portions together in a tight configuration.  
         [0034]     In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed.  
         [0035]     Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.