Double wall duct connector

A double wall round or oval duct system assembly having an outer duct connector, an inner duct connector and a closure ring is provided. The inner duct connector of the duct assembly has an adhesive applied on the transverse flange face of its transverse flange thus allowing a sealing connection between the inner and outer duct connectors upon compression with the closure ring. The double wall round or oval duct system assembly will improve the efficiency and will reduce or eliminate air leakage upon connection of two round or oval duct segments. A method of installing the assembly system is also provided.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to a method and apparatus for connecting double wall round and oval duct segments used in the heating, ventilating, exhaust and/or air conditioning fields.

Description of Related Art

Double wall ducts having round or oval cross sectional shape are used to transport heated or cooled air or other gasses from one place to another. A typical example is when heated or cooled air from an air conditioner or furnace is transported to individual locations by a system of ducts, which includes ducts segments connected to each other at their ends. When adjacent duct segments are connected, flanges, collar, clamps, sleeves, and other removable fastening methods have been used.

Double wall, insulated duct work is used when insulation is desired within a duct system. For double wall duct work, connectors have been used that possess adjacent flanges thereby providing rigidity across the connection. Duct segments often have cross-sections of varying dimensions. Thus, when adjacent double wall duct segments are connected with solid continuous double-flanged connectors, it may be difficult to provide a good connection between ducts having different cross-sectional dimensions or diameters. This is often times due to tolerance variations between both the duct connector and duct segment manufacturers

In contrast, when non-flanged connectors are used to connect circular or oval adjacent duct segments, the resulting connection may result in the bending or loss of shape at the connection.

Attaching connectors to duct work segments often involves the use of heat such as via welding. If the connection also requires the use of a sealant material at the connector and duct work segment, the use of heat may result in the melting or dripping of the sealant.

When this occurs with these types of connectors, they may not be effective at maintaining the forced air inside the duct, i.e., without leaking through the connection.

Accordingly, there is a need for an improved double wall duct connector for round or oval duct work systems, which does not require rigid connector pieces, which maintain the original round or oval duct shape, and which does not require the use of heat to make the connection to install the connector piece.

BRIEF SUMMARY OF THE INVENTION

This invention provides an apparatus for assisting in the connection of adjacent double wall round or oval duct segments. The apparatus comprises outer round or oval duct connectors each having an inner leg, at least one vertex and an outer transverse flange on at least one end of each outer duct segment. The outer transverse flange extends substantially perpendicularly from the inner leg and has a transverse flange mating face directed away from the inner leg. The apparatus also comprises inner round or oval duct connector each having an inner leg, at least one vertex and an inner transverse flange on the at least one end of each inner duct segment. The inner transverse flange substantially circumscribes the associated end and extends substantially perpendicularly from the inner leg and having a transverse flange face directed toward the inner leg. An adhesive is dispensed on the transverse flange face of the inner transverse flange. The apparatus further comprises a closure ring placed over the outer transverse flanges and inner transverse flanges of mating duct connectors with the transverse flange face of the inner transverse flange and the transverse flange mating face of the outer transverse flange being maintained in contact by the adhesive.

This invention also provides for a method for connecting adjacent double wall round or oval duct segments. The method of the present invention comprises providing double wall round or oval duct segments in need of connection. The method of the present invention further comprises providing outer round or oval duct connectors each having an inner leg, a leading edge, vertex and an outer transverse flange on one end of each outer duct segment. The outer transverse flange extends substantially perpendicularly from the inner leg and has a transverse flange mating face directed away from the inner leg. The method further comprises providing inner round or oval duct connectors each having an inner leg, a leading edge, a vertex and one inner transverse flange on one end of each inner duct segment. The inner transverse flange substantially circumscribes the associated end and extends substantially perpendicularly from the inner leg. The inner transverse flange has a transverse flange face directed toward the inner leg and an adhesive is disposed on its face. The method further comprises the step of inserting the leading edge of the outer duct connectors in the round or oval duct segments in need of connection. The method then provides the step of inserting the leading edge of the inner duct connectors in the round or oval duct segments in need of connection. The method also comprises abutting the outer transverse flange of the outer duct connector to the adhesive of the inner transverse flange of the inner duct connector to substantially align the inner volumes of the adjacent duct segments. The method further comprises placing a closure ring over the inner transverse flanges and outer transverse flanges of mating duct connectors with the transverse flange face of the inner transverse flange and the transverse flange mating face of the outer transverse flange being put in contact by the adhesive, the closure ring comprising fastening means. The method further comprises fastening the closure ring to form a seal between the inner and outer duct sections.

This invention also provides a double wall round or oval duct connector that is easy for an installer to use and that provides adequate connection between adjacent insulated round or oval duct segments. More particularly, the present invention provides a universal, self-contained, tool or fastener free design and incorporates a rapid-bonding, self-sealing insulation shield and connector design for double wall round or oval HVAC duct. The corresponding method of installing such a double wall round or oval duct connector is also provided.

DETAILED DESCRIPTION

As used herein, a non-limiting example of the term duct segment includes a cylindrical tube used to transport air such as round and oval ducts.

As used herein a non-limiting example of the term round duct segment includes a cylindrical tube used to transport air having a round circumference.

A non-limiting example of the term ductwork includes straight pieces of duct, duct segments, duct connectors, and all types of fittings.

As used herein, a non-limiting example of the term double wall duct segment includes an inner duct segment—or interior duct wall—and an outer duct segment—or exterior duct wall—separated by a layer of insulating material.

As used herein, a non-limiting example of the term adjacent duct segments includes pieces of double wall duct that are to be joined together.

As used herein, a non-limiting example of the terms gasket or gasket material includes any type of sealing or adhesive material that reduces air leakage between the joints of a ductwork.

As used herein, a non-limiting example of the term sealed connection includes a ductwork connection or joint between double wall duct segments, including the inner and outer duct segments, that has less leakage than a ductwork connection or joint without an adhesive or adhesive material between double wall duct segments and allows for the connection to be maintained without loss of shape. A non-limiting example of adhesive, which may be used to sealingly connect inner and outer double wall duct segments, is double sided tape.

As used herein, a non-limiting example of the term, the term circumferential adjustment split includes a split or cut along the axis in the duct segment or connector, thus allowing for the segment or connector's diameter to be adjusted.

FIG. 1shows the assembly100of two double wall round duct segments110and120connected by the connecting apparatus130. The double wall round duct segments110and120are generally cylindrical sheet metal bodies with outwardly projecting spiral ribs105on the outside at evenly spaced intervals along their lengths. The double wall round duct segments contain a layer of insulating material112between an interior duct wall114and an exterior duct wall116. As later discussed in detail, the round duct segments are described as having a generally circular configuration. It should be understood, however, that the apparatus of the present invention applies also to corresponding oval duct segments.

FIG. 2shows a view of apparatus200along the center axis parallel to the airstream inFIG. 1.

FIG. 3is a sectional view illustrating the connector apparatus generally designated by the numeral300for connecting two double wall round duct segments310and320each having exterior duct walls311and321, respectively, and interior duct walls313and323, respectively. Each segment comprises two duct walls separated by insulation material315having an insulation thickness C. The connecting apparatus includes two outer round duct connectors340each having an inner leg342. The outer round duct connectors each have at the vertex344an outer transverse flange346. The outer transverse flange extends substantially perpendicularly from the inner leg342and has a transverse flange mating face348directed away from the inner leg342. The apparatus for connecting the two round duct segments also comprises two inner round duct connectors350each having an inner leg352. The inner round duct connectors each have at the vertex354an inner transverse flange356. The inner transverse flange356substantially circumscribes the associated vertex354and extends substantially perpendicularly from the inner leg352and has a transverse flange face358directed toward the inner leg352. An adhesive360is disposed on the transverse flange face358of the inner transverse flange350. The apparatus further comprises a closure ring330placed over the outer transverse flanges346and inner transverse flanges356of mating duct connectors340and350with the transverse flange face358of each inner transverse flange sealingly connected with the transverse flange mating face348of each outer transverse flange by the adhesive360. As shown inFIG. 3, the adhesive is not exposed and does not come into contact with the airstream.

A suitable amount of gasket370may be placed in annular void372to provide a sealed connection between the outer transverse flanges346of mating outer duct connectors340and/or between the inner transverse flanges356of mating inner duct connectors350. As seen inFIG. 3, gasket material370is placed in annular void372, and mating transverse flanges346, which are adhesively connected to mating transverse flanges356, are embedded in the gasket370upon compression under the closure ring330. In addition to the adhesive connecting the transverse flange faces of the transverse flanges of the inner and outer duct connectors, the gasket material370provides an airtight seal to further ensure that air passing through the connection between round duct segments310and320does not escape through annular void372to the atmosphere.

As shown in the configuration illustrated inFIG. 3, the connection between the round duct segments310and320provides an excellent seal. With this configuration, the resulting connection is such that vibrations are reduced and the connection is capable of a pipe pressure of at least 18″ w.g. positive and −10″ w.g negative without the adhesive failing. In addition, the seal provided by the use of adhesive, which may be double sided tape, between the transverse flange faces of the inner transverse flange and the outer transverse flange of each mating inner and outer duct connector allows for the cross-sectional dimensions or diameters of adjacent duct segments310and320to be maintained without loss of shape upon connection between such segments.

When assembling adjacent duct segments310and320using inner and outer round duct connectors350and340, respectively, and a closure ring330to provide a completed connection of a double wall round duct system assembly300, the following steps are provided.

First, two double wall round duct segments310and320in need of connection are provided. Outer round duct connectors340, each having an inner leg342, a vertex344, a leading edge345and an outer transverse flange346extending from vertex344of each outer duct connector340, are also provided. The outer transverse flange346extends substantially perpendicularly from the inner leg342and has a transverse flange mating face348directed away from the inner leg342. The method further comprises providing inner round duct connectors350each having an inner leg352, a vertex354, a leading edge355, and one inner transverse flange356extending from vertex354of each inner duct connector350. The inner transverse flange356substantially circumscribes the associated vertex354and extends substantially perpendicularly from the inner leg352. The inner round duct connector350can be separate and not connected to outer round duct connector340when provided. The inner transverse flange356has a transverse flange mating face358directed toward the inner leg352and an adhesive360is disposed on its transverse flange mating face358. The method further comprises the step of inserting the leading edges345of the outer duct connectors in the exterior duct walls311and321of round duct segments310and320in need of connection. The method then provides the step of inserting the leading edge355of the inner duct connectors in the interior duct walls313and323of the round duct segments310and320in need of connection. The method also comprises abutting the transverse flange mating face of the outer transverse flange346of the outer duct connector340to the adhesive360on the transverse flange face of the inner transverse flange356of the inner duct connector350to substantially align the inner volumes of the adjacent round duct segments310and320. The method further comprises placing a closure ring330over the inner transverse flanges356and outer transverse flanges346of mating round duct sections350and340with the transverse flange face of the inner transverse flange356and the transverse flange mating face of the outer transverse flange346being put in contact by the adhesive360, the closure ring may comprise fastening means, which are known in the art and may include a clamp-type mechanism, for example. The method further comprises fastening the closure ring to complete and secure the two duct segments and to form a seal between the inner air stream and outer atmosphere duct sections. The fastening of the closure ring results in compression of gasket370and of the adhesive360between the inner and outer transverse flange faces of the duct connectors thus allowing for an excellent sealing connection.

FIG. 4is a partial sectional view of a connection apparatus400similar to that shown inFIG. 3but illustrating the exposed edges of the outer transverse flange446of the outer duct connectors440sealingly embedded in gasket material470when the inner transverse flanges456of the inner duct connectors450do not match the length of the outer transverse flanges446of the outer duct connectors440. In this configuration, the adhesive460provides a sealed connection between the outer transverse flanges346and the corresponding inner transverse flanges356of mating duct connectors340and350. A closure ring430is placed over the outer transverse flanges346and inner transverse flanges356, providing a seal between round duct segments410and420having an insulation thickness D. The round duct segments may have interior411and exterior413duct walls separating the insulation material415, with varying insulation thickness D, while still allowing the adhesive460to seal the inner and outer transverse flanges together as illustrated inFIG. 4.

As illustrated inFIGS. 5 and 6, the inner round duct section350ofFIG. 3may include a circumferential adjustment split380allowing the inner leg352of the inner duct connector to be slidably positioned in the circular interior duct end portion of the round duct segment in need of connection, the circumferential adjustment split being utilized allows to increase or decrease the diameter of the duct connector, thus allowing adapting the diameter of the inner duct connector to the diameter of the corresponding round duct segment.

FIGS. 5 and 6also illustrate the use of double-sided adhesive360on the inner transverse flange of the inner duct connector. In particular, the adhesive360may be a unitary piece disposed about the periphery of the transverse flange face of the inner transverse flange356. Furthermore, the adhesive may be such that its surface area is smaller than the surface area of the transverse flange face358of the inner transverse flange and is disposed on the outer perimeter of the transverse flange face of the inner transverse flange.

The following examples and accompanyingFIG. 7will further explain the invention.

EXAMPLES

To compare the leakage of a SPIRALMATE® connection with inner ring (attached with BNGASKET) to a standard SPIRALMATE® connection (without inner ring) to determine if BNGASKET is an acceptable attachment method. This will be achieved over several tests required.

All tests will be done with a two connection system per SMACNA requirements. The tests performed will be leakage trials for Standard SPIRALMATE® connection and Standard SPIRALMATE® connection with inner ring connected with double-sided tape/gasket. This will be trialed for both small and large profile SPIRALMATE® connections.

The following material and instrumentation were used:

The following are the test samples described herein:

Installation

Connect the Cadillac Products blower unit to the Meriam laminar flow element then to the duct mock-up. Make sure the Extech Differential Pressure Manometer is connected to the Meriam laminar flow element and the Retrotec Digital Manometer is ported into the beginning of the duct mock-up (see FIGS. 5-2 page 5-3 in the “SMACNA HVAC Air Duct Leakage Test Manual,” incorporated by reference in its entirety herein).

The duct mock-up will consist of three sections equivalent in length connected together by the SPIRALMATE® trials that are attached with #10 Tek screws around the circumference and sealed. Make sure all joints, not including the actual SPIRALMATE® connection, are sealed with proper sealant to avoid leaks.

Test Procedural Definitions:

Use the Cadillac Products blower unit to induce a positive and negative pressure inside the duct mock-up. Use the Meriam laminar flow element to measure the airflow at −10 in and +10 in WG pressure in increments. Repeat this for all connections.

Test and record the large standard SPIRALMATE® connection. Assemble as listed in the installation instructions on the product spec sheet.

Test and record the large standard SPIRALMATE® connection with the inner ring attached using BNGASKET to connect it (attach in segments of tape approx. 3.0″ long eq. spaced, 8 pcs). Assemble as listed in the installation instructions on the product spec sheet.

Test and record the small standard SPIRALMATE® connection. Assemble as listed in the installation instructions on the product spec sheet.

Test and record the small standard SPIRALMATE® connection with the inner ring attached using BNGASKET to connect it (attach in segments of tape approx. 3.0″ long eq. spaced, 4 pcs). Assemble as listed in the installation instructions on the product spec sheet.

Test Results

The test results are provided in the following Tables (Tables 1-4) and accompanying Figures (FIGS. 7-11).

The results of this round of testing were much more consistent and accurate than the first attempt. Minimal leakage was observed (if any) in every test sample. For 10″ diameter connections, leakage values ranged from −0.233 to 0.351 CFM, with negligible differences between connections with and without the inner rings. For 36″ diameter connections, leakage values ranged from −0.110 to 0.326 CFM, with negligible differences between connections with and without inner rings.

Negative leakage values typically result from an inaccurate tare due to % error in equipment or inherent uncontrollable variables in the system. All leakage values are low enough to conclude that there were no major flaws in the system or the test method. Additionally, it was evident that there are no major differences (in terms of leakage) between the two sizes (10″ & 36″) or between the types of connections (with and without inner rings).

Overall, BNGASKET adhered better than the other tapes (trialed in first round of tests). Due to the cost and overall performance, it was determined that BNGASKET serves as an acceptable method for attaching the inner ring to the SPIRALMATE® flange.

There are two primary objectives to this series of tests. First is to compare the leakage of a SPIRALMATE® connection with centered inner rings (attached with ½″ PSA Tape) using double-wall duct to a similar connection with non-centered inner rings. Second is to compare the leakage of a SPIRALMATE® connection using double-wall duct where flange and inner ring splices are misaligned vs. aligned.

All tests will be done with a one-connection system. The tests performed will be leakage trials for a standard SPIRALMATE® connection with inner rings attached (concentric vs. non-concentric & aligned vs. misaligned splices) using ½″ double-sided tape/gasket. Only large profile SPIRALMATE® connections will be used, due to the diameter of duct being tested. The application of the inner rings on large diameter double-wall duct will also be trialed for determining difficulty.

The following material and instrumentation were used:

Connect the Cadillac Products blower unit to the Meriam laminar flow element then to the duct mock-up. Make sure the Extech Differential Pressure Manometer is connected to the Meriam laminar flow element and the Retrotec Digital Manometer is ported into the beginning of the duct mock-up (see FIG. 5-2 page 5-3 in the “SMACNA HVAC Air Duct Leakage Test Manual”).

The duct mock-up will consist of two sections equivalent in length connected together using the SPIRALMATE® system, attached with #10 Tek screws around the circumference and sealed. Make sure all joints, not including the actual SPIRALMATE® connection, are sealed with proper sealant to avoid leaks.
Test Procedural Definitions:

Use the Cadillac Products blower unit to induce a positive and negative pressure inside the duct mock-up. Use the Meriam laminar flow element to measure the airflow between −10 in and +10 in WG pressure in 2-in increments. Repeat this for all connections.

Test and record leakage of the large SPIRALMATE® connection with non-centered inner ring and aligned splices, using ½″ PSA tape.

Test and record leakage of the large SPIRALMATE® connection with centered inner ring and misaligned flange & inner ring splices, using ½″ PSA tape.

The test results are provided in Table 1 and accompanyingFIG. 12.

Based on the above data and the graph ofFIG. 12, it appears that there is no noticeable difference (in terms of leakage) between the centered/misaligned system and the non-centered/aligned system. With leakage values this low, considering the error in accuracy of the measuring equipment itself, leakage differences between the different (tested) assembly methods can be considered negligible.

When attaching the inner ring to the SPIRALMATE® flange, it is much easier to allow the inner ring to follow its natural shape, rather than trying to bend the ring to follow the flange edge. Due to the weight of the inner duct wall and insulation, it was somewhat difficult to force the inner ring to conform to the imperfections of the duct to keep it concentric. This seems to be more apparent as the duct diameter increases and the duct profile takes on more of an oval shape. However, as shown by the test, forcing the inner ring to be concentric with the duct does not affect leakage to a measurable degree.

Various changes could be made in the above apparatus 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 above description, as shown in the accompanying drawings, shall be interpreted as illustrative and not as a limitation.