Patent Description:
The present disclosure generally relates to fittings for connecting flexible ducts in heating, ventilation, and air conditioning (HVAC) applications. More specifically, the present disclosure is related to a fitting assembly, a ferrule, a ductwork assembly, and a method of connecting a flexible duct to a fitting and/or ferrule.

Non-rigid ducting is widely used in residential and commercial HVAC applications to economically install long sections of ductwork in substantially straight lines or large-radius curves. However, rigid fittings must be used where tight curves are required or where the ducting connects to other components of the HVAC system. Conventionally, such rigid fittings are made of sheet metal and require the use of mastic and/or mechanical fasteners to ensure a solid and air-tight seal with the ducting, adding labor and material expense to the installation process. This is largely due to the inconsistency of sheet metal fittings, and their inherently leaky stamped construction. Moreover, spreading or spraying mastic on all sides of ductwork is challenging as the ductwork is often installed in tight chases and cavities with no access to the obscured side. Additionally, because of the sharp edges and design of conventional sheet metal fittings, it is often difficult to stretch ductwork over the fitting. Exacerbating these issues is that the large diameter of conventional ducting makes it difficult to hold both the ducting and the fitting when making the necessary connections. Once the ducting is stretched over the fitting, the installer must attach zip ties and screws while working against the tension of the duct. Often this requires several tries from the installer to finish the connection. Additionally, because the connection generally must be made while the ducting is under tension, it is difficult to properly stretch the duct to length as the ducting inherently pulls itself back to its natural state. An example of a suitable fitting is described in <CIT> describing a combination of an air hose and a connecting piece which projects into the air hose, the connecting piece tapering into the hose in the shape of a truncated cone and having radially projecting ribs on its outer surface which engage with the inner wall of the tube.

In view of the foregoing, there still exists a need for ductwork assemblies, components thereof, and methods of assembling a ductwork assembly that simplify the process of installing ductwork.

Embodiments of the present disclosure are directed to a fitting assembly for connection to a flexible duct. Insofar as the term embodiment or aspect or alternative is used in the following, or features are presented as being optional, this should be interpreted in such a way that the only protection sought is that of the invention claimed and defined in the appended claims.

The fitting assembly according to the invention includes a ferrule configured for insertion into an open end of the flexible duct. The ferrule may include a sidewall defining a minor diameter and a major diameter spaced apart from the minor diameter, and a ferrule thread extending radially outward from the sidewall. The fitting assembly may further include a fitting removably connected to the ferrule. The minor diameter is less than or equal to an inner diameter of the flexible duct with the flexible duct in an untensioned state. The major diameter is greater than the inner diameter of the flexible duct with the flexible duct fully elongated. One of the fitting and the ferrule defines a recess. Another of the fitting and the ferrule includes a tab configured to extend into the recess. One of the recess and the tab includes an edge. Another of the recess and the tab includes a ramped surface extending in a circumferential direction of the ferrule, such that rotation of the ferrule relative to the fitting causes the ramped surface to engage the edge, thereby radially deflecting the tab and disengaging the tab from the recess.

In some embodiments, the recess is formed in an external surface of the fitting.

In some embodiments, engagement of the tab and the recess limits rotation of the ferrule relative to the fitting about the longitudinal axis of the ferrule and the fitting when a rotational force applied to the ferrule relative to the fitting is less than a force required to radially deflect the tab.

In some embodiments, the ferrule includes a grip for assisting a user in grasping the ferrule during at least one of connection of the ferrule to the flexible duct, and connection of the ferrule to the fitting.

In some embodiments, the ferrule thread includes a discontinuous portion.

In some embodiments, the discontinuous portion includes a break extending from a crest of the ferrule thread to the sidewall of the ferrule. The break is configured to bite into the flexible duct to prevent unthreading of the flexible duct from the ferrule thread.

In some embodiments, the discontinuous portion includes a ramped surface extending from the sidewall of the ferrule to a crest of the ferrule thread.

In some embodiments, the ferrule further includes a circumferential depression for receiving a terminal end of the flexible duct.

In some embodiments, the fitting assembly further includes a clamp surrounding the circumferential depression and configured to clamp the flexible duct to the ferrule.

In some embodiments, a taper of the sidewall of the ferrule is configured to stretch a sheet material of the flexible duct as the ferrule is threaded into the flexible duct.

In some embodiments, a pitch of the ferrule thread is less than or equal to a pitch of a helix structure of the flexible duct with the flexible duct fully elongated.

In some embodiments, an outer diameter of the ferrule thread is larger than an inner diameter of a helix structure of the flexible duct when a pitch of the ferrule thread is equal to a pitch of the helix structure.

In some embodiments, the connection between the fitting and the ferrule is substantially air tight without application of a sealant material.

In some embodiments, the fitting assembly further includes a gasket or sealant material disposed at an interface of the fitting and the ferrule.

In some embodiments, the fitting includes at least one of an elbow, a tee, a wye, a manifold takeoff, a coupling, a terminal boot, a cap, a plug, a union, and a flange.

Other embodiments of the present disclosure are directed to a ferrule for connecting to a flexible duct. The ferrule includes a sidewall defining a minor diameter and a major diameter spaced apart from the minor diameter and a ferrule thread extending radially outward from the sidewall. The ferrule may further include at least one of a tab configured to extend into a recess of a fitting, the tab configured to radially deflect and disengage from the recess of the fitting upon rotation of the ferrule relative to the fitting; and a recess configured to receive a tab of the fitting, the recess configured to radially deflect the tab of the fitting upon rotation of the ferrule relative to the fitting. The minor diameter is less than or equal to an inner diameter of the flexible duct with the flexible duct in an untensioned state. The major diameter is greater than the inner diameter of the flexible duct with the flexible duct fully elongated.

In some embodiments, engagement of the tab with the recess of the fitting limits rotation of the ferrule relative to the fitting about the a longitudinal axis of the ferrule and the fitting when a rotational force applied to the ferrule relative to the fitting is less than a force required to radially deflect the tab.

In some embodiments, the discontinuous portion includes a break extending from a crest of the ferrule thread to the sidewall, wherein the break is configured to bite into the flexible duct to prevent unthreading of the flexible duct from the ferrule thread.

In some embodiments, the discontinuous portion includes a ramped surface extending from the sidewall to a crest of the ferrule thread.

In some embodiments, a taper of the sidewall is configured to stretch a sheet material of the flexible duct as the flexible duct is threaded onto the ferrule thread.

In some embodiments, a pitch of the ferrule thread is less than a pitch of a helix structure of the flexible duct with the flexible duct fully elongated.

Other embodiments of the present disclosure are directed to a ductwork assembly including a duct having a helix structure and a flexible sheet material surrounding the helix structure. The ductwork assembly may further include a ferrule including a sidewall defining a minor diameter and a major diameter spaced apart from the minor diameter and a ferrule thread extending radially outward from the sidewall. The ferrule may include at least one of a tab configured to extend into a recess of a fitting, the tab configured to radially deflect and disengage from the recess of the fitting upon rotation of the ferrule relative to the fitting; and a recess configured to receive a tab of the fitting, the recess configured to radially deflect the tab of the fitting upon rotation of the ferrule relative to the fitting. The minor diameter is less than or equal to an inner diameter of the flexible duct with the flexible duct in an untensioned state. The major diameter is greater than the inner diameter of the flexible duct with the flexible duct fully elongated. The helix structure of the duct is threaded over the ferrule thread such that the flexible sheet material of the duct is stretched radially outward by the sidewall of the ferrule.

In some embodiments, the ductwork assembly further includes a fitting removably connected to the ferrule. The fitting includes at least one of an elbow, a tee, a wye, a manifold takeoff, a coupling, a terminal boot, a cap, a plug, a union, and a flange.

Further details and advantages of the present disclosure will be understood from the following detailed description read in conjunction with the accompanying drawings.

For purposes of the description hereinafter, the terms "end," "upper," "lower," "right," "left," "vertical," "horizontal," "top," "bottom," "lateral," "longitudinal," and derivatives thereof shall relate to the invention as it is oriented in the drawing figures. However, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments or aspects. Hence, specific dimensions and other physical characteristics related to the embodiments or aspects disclosed herein are not to be considered as limiting.

All numbers used in the specification and claims are to be understood as being modified in all instances by the term "about". The terms "approximately", "about", and "substantially" mean a range of plus or minus ten percent of the stated value. Ranges of values are to be understood as being inclusive unless specified to the contrary.

As used herein, the term "at least one of" is synonymous with "one or more of". For example, the phrase "at least one of A, B, and C" means any one of A, B, and C, or any combination of any two or more of A, B, and C. For example, "at least one of A, B, and C" includes one or more of A alone; or one or more of B alone; or one or more of C alone; or one or more of A and one or more of B; or one or more of A and one or more of C; or one or more of B and one or more of C; or one or more of all of A, B, and C. Similarly, as used herein, the term "at least two of" is synonymous with "two or more of". For example, the phrase "at least two of D, E, and F" means any combination of any two or more of D, E, and F. For example, "at least two of D, E, and F" includes one or more of D and one or more of E; or one or more of D and one or more of F; or one or more of E and one or more of F; or one or more of all of D, E, and F.

As used herein, the term "flexible duct" means a non-rigid, elongate hollow structure suitable for the conveyance of fluid such as air. As will be described in greater detail herein, embodiments of the flexible duct may be radially and/or axially deformable. The flexible duct may be transitionable between several physical states in response to axial and/or radial loading. A relaxed or natural state of the flexible duct refers to a state assumed by the flexible duct when no axial or radial load is applied. An elongated, tensioned, or pretensioned state of the flexible duct refers to a state in which at least a portion of the duct is axially extended to be longer than the relaxed state. The elongated, tensioned, or pretensioned state may be assumed by the flexible duct in response to an axial and/or radial load. A compressed state of the flexible duct refers to a state in which at least a portion of the duct is axially compressed to be shorter than the relaxed state. The compressed state may be assumed by the flexible duct in response to an axial and/or radial load. In some embodiments, the relaxed or natural state of the flexible duct may also correspond to the maximum extended length of the flexible duct, in which case the elongated state of the flexible duct would be the same as the natural state. In some embodiments, the flexible duct may be in the elongated, tensioned, or pretensioned state when the flexible duct is installed in a ductwork system. The flexible duct may be un-insulated, or have a thermally insulating layer surrounding the inner air conduit.

As used herein, the terms "air tight" and "substantially air tight", when used to define an interface or connection between two or more members, means that a total volume of air that leaks from the interface in one hour is less than <NUM> times the volume of a test sample which includes <NUM> feet of duct connected to the interface and pressurized to <NUM> Pa.

Referring now to the drawings, in which like reference characters refer to like parts throughout the several views thereof, various embodiments of a fitting assembly, a ferrule, and a ductwork assembly are shown. Referring now to <FIG>, a ductwork assembly <NUM> is illustrated which includes at least one flexible duct <NUM> connected to a fitting assembly <NUM> which includes a fitting <NUM> and at least one ferrule <NUM>. The fitting assembly <NUM> may be used to join sections of flexible duct <NUM> in the ductwork assembly <NUM>. The ductwork assembly <NUM> may form a part of a residential or commercial HVAC system or other fluid distribution system. For example, the ductwork assembly <NUM> may convey air from a furnace, heat pump, or air conditioner to a register. The ductwork assembly <NUM> shown in <FIG> is only a portion of an HVAC system which may include a plurality of flexible ducts <NUM>, fitting assemblies <NUM>, and other components such as registers, furnaces, heat pumps, air conditioners, humidifiers, fans, other air-consuming appliances, and the like. Additional details of an HVAC system in which the ductwork assembly <NUM> may be utilized is described in International Patent Application Publication No. <CIT>.

As may be appreciated from <FIG>, the flexible duct <NUM> extends along a longitudinal axis LD and defines a hollow interior <NUM> suitable for the conveyance of fluid such as air. In particular, a sidewall of the flexible duct <NUM> is formed of a flexible sheet material <NUM> which extends along the longitudinal axis LD and surrounds the hollow interior <NUM>. The flexible duct <NUM> may have a generally circular in cross section and, at least in the relaxed state, has substantially continuous inner and outer diameters along the longitudinal axis LD. In some embodiments, the flexible duct <NUM> includes a resilient helix structure <NUM> embedded in, surrounding, or surrounded by the flexible sheet material <NUM>. In the embodiment shown in the drawings, the helix structure <NUM> includes a helical wire. In other embodiments, the helix structure <NUM> may include a helical crimp extended around an outer surface of the flexible sheet material <NUM> and crimping or pinching a portion of the flexible sheet material <NUM> along the path of the helical crimp. In some embodiments, the flexible duct <NUM> may include multiple helix structures <NUM>, though for the purposes of this disclosure a single helix structure <NUM> will be assumed for simplicity. The helix structure <NUM> is resiliently deformable and includes a plurality of continuous windings or revolutions.

With continued reference to <FIG> and further reference to <FIG> and <FIG>, the fitting assembly <NUM> includes a ferrule <NUM> having a sidewall <NUM> which connects to a terminal end <NUM> of the flexible duct <NUM>. With the flexible duct <NUM> connected to the ferrule <NUM>, the ferrule shares and is coaxial with the longitudinal axis LD of the flexible duct <NUM>. The sidewall <NUM> of the ferrule extends from a first end <NUM> of the ferrule <NUM> configured for insertion into the flexible duct <NUM> to a second end <NUM> of the ferrule <NUM> configured for connection to the fitting <NUM>. The sidewall <NUM> has a radially increasing taper from the first end <NUM> of the ferrule <NUM> to the second end <NUM> of the ferrule <NUM>, such that the sidewall <NUM> defines a minor diameter Dmin adjacent the first end <NUM> of the ferrule <NUM> and a major diameter Dmaj axially spaced apart from the minor diameter Dmin along the sidewall <NUM>. The ferrule <NUM> thus forms a frustoconical structure between the minor and major diameters Dmin, Dmaj thereof.

The ferrule <NUM> further includes at least one thread <NUM> extending radially from the sidewall <NUM>. In some embodiments, the at least one thread <NUM> may extend for at least one revolution around the sidewall <NUM> of the ferrule <NUM>. The at least one thread <NUM> is configured to engage the flexible duct <NUM> to retain the flexible duct <NUM> on the ferrule <NUM>. The engagement of the ferrule <NUM> with the flexible duct <NUM> will now be described with reference to <FIG>. As noted herein, the flexible duct <NUM> may be transitionable between a natural state, an elongated state, and a compressed state. More particularly, the helix structure <NUM> may be resilient such that radial and/or axial loading applied to the helix structure <NUM> induces the flexible duct <NUM> to assume either the elongated or compressed state, depending on the direction of the applied load. In the elongated state, the distance between adjacent windings of the helix structure <NUM> may be defined by an elongated pitch PE, whereas, in the compressed state, the distance between adjacent windings of the helix structure <NUM> may be defined by a compressed pitch Pc which is less than the elongated pitch PE. An example of a radial load capable of inducing the compressed state is a load applied on the helix structure <NUM> by sliding the helix structure <NUM> over a conical structure having a greater diameter than the helix structure <NUM>. This radial loading causes the individual windings of the helix structure <NUM> to expand in diameter and also causes the helix structure <NUM> to compress along the longitudinal axis LD, thereby reducing the distance between adjacent windings relative to the elongated state. The helix structure <NUM> is resilient in that the helix structure <NUM> returns to the natural state upon removal of the load that induced the elongated or compressed state.

To engage the ferrule <NUM> with the terminal end <NUM> of the flexible duct <NUM>, the helix structure <NUM> is threaded onto the at least one thread <NUM> of the ferrule <NUM> by rotating the flexible duct <NUM> relative to the ferrule, or vice versa. The helix structure <NUM> engages the at least one thread <NUM> to advance the flexible duct towards the second end <NUM> of the ferrule <NUM> as the flexible duct is rotated relative to the ferrule <NUM>. More particularly, the at least one thread <NUM> engages and radially stretches the flexible sheet material <NUM> as the helix structure <NUM> rides along a shank <NUM> of the thread <NUM>. The minor diameter Dmin of the sidewall <NUM> is less than an inner diameter of the flexible duct <NUM>, such that the helix structure <NUM> fits around the first end <NUM> of the ferrule <NUM> without being radially deformed by the sidewall <NUM>. The major diameter Dmaj of the sidewall <NUM> is greater than the inner diameter of the flexible duct <NUM>, such that as the flexible duct <NUM> is threaded onto the ferrule <NUM> toward the second end <NUM>, the sidewall <NUM> forces the helix structure <NUM> to radially expand. Consequently, a portion of the helix structure <NUM> forced to radially expand assumes the compressed state and the compressed pitch Pc, whereas a portion of the helix structure <NUM> that fits over the sidewall <NUM> without being radially deformed maintains the elongated state and the elongated pitch PE. The flexible duct <NUM> may be threaded onto the ferrule <NUM> such that at least one revolution or winding of the helix structure <NUM> engages and is deformed by the sidewall <NUM> of the ferrule. Threading the flexible duct <NUM> onto the ferrule <NUM> may be performed by hand such that a user can rapidly and securely assemble the ductwork assembly <NUM> without the need for specialized tools or advanced training.

The radial load applied to the flexible duct <NUM> by the ferrule <NUM> results in an interference fit between the ferrule <NUM> and the flexible duct <NUM>, causing the flexible duct <NUM> to be retained on the ferrule <NUM>. In some embodiments, the interference fit may be sufficient to withstand an axial pullout force of <NUM>,<NUM> (<NUM> pounds). Thus, the interference fit between the ferrule <NUM> and the flexible duct <NUM> may be sufficient to secure the flexible duct <NUM> to the ferrule <NUM> in the completed, operational ductwork assembly <NUM>. In some embodiments, an adhesive may be applied between the flexible duct <NUM> and the ferrule <NUM> to assist in securing the flexible duct <NUM> to the ferrule <NUM>. In some embodiments, the interface between the ferrule <NUM> and the flexible duct <NUM> is air tight, such that additional sealing components or materials such as clamps, fasteners, gaskets, mastics, and/or sealants need not be applied to the interface. In other embodiments, one or more of such sealing components or materials may be applied to the interface between the ferrule <NUM> and the flexible duct <NUM>.

With continued reference to <FIG> and <FIG>, a pitch PF defined by the spacing between adjacent windings of the at least one thread <NUM> of the ferrule <NUM> may be equal to or less than a pitch of the helix structure <NUM>. In some embodiments, the pitch PF may be approximately equal to the compressed pitch Pc of the helix structure <NUM>, to facilitate a tight connection between the at least one thread <NUM> and the portion of the helix structure <NUM> in the compressed state. An outer diameter OD of the at least one thread <NUM> may be greater than the inner diameter of the flexible duct <NUM> with the flexible duct <NUM> installed on the ferrule <NUM>. As such, the at least one thread <NUM> may engage the flexible duct <NUM> even in the vicinity of the minor diameter Dmin of the sidewall <NUM> where the sidewall <NUM> does not engage the flexible duct <NUM>. In particular, the outer diameter OD may be larger than an inner diameter of the helix structure <NUM> when the pitch PF of the at least one thread <NUM> is equal to a compressed pitch Pc with the helix structure <NUM> engaging the sidewall <NUM> of the ferrule <NUM>. As such, the helix structure <NUM> is prevented from compressing further due to abutment of the helix structure with the at least one thread <NUM>, thereby preventing radial expansion of the helix structure <NUM> and preventing the helix structure <NUM> from being able to jump the at least one thread <NUM>.

In some embodiments, the outer diameter OD of the at least one thread <NUM> may be substantially constant along the length of the sidewall <NUM>. In order that the outer diameter OD of the at least one thread <NUM> may be substantially constant despite the tapering of the sidewall <NUM>, the flank <NUM> of the at least one thread <NUM> may be longer towards the first end <NUM> of the ferrule <NUM> and shorter towards the second end <NUM> of the ferrule <NUM>.

In some embodiments, the at least one thread <NUM> may extend for at least one revolution, at least two revolutions, or more revolutions around the sidewall <NUM>. In some embodiments, the flexible duct <NUM> may be threaded onto the ferrule <NUM> so as to engage the entirety of the at least one thread <NUM>, while in other embodiments the flexible duct <NUM> may be threaded onto the ferrule <NUM> so as to engage only a portion of the at least one thread <NUM>. The number of revolutions of the at least one thread, the outer diameter OD of the at least one thread, and the degree to which the flexible duct <NUM> engages the at least one thread <NUM> may be selected to achieve a desired pullout resistance of the ferrule <NUM>. For example, the desired pullout resistance may be <NUM>,<NUM> N (<NUM> pounds-force).

With continued reference to <FIG>, in some embodiments, the at least one thread <NUM> may include a discontinuous section at which the shank <NUM> does extend from the sidewall <NUM> of the ferrule <NUM>, or at which the height of the shank <NUM> is reduced relative to adjacent portions of the at least one thread <NUM>. A first end of the discontinuous portion of the at least one thread <NUM> may include a break <NUM> extending from a crest of the at least one thread <NUM> to the sidewall <NUM>. The break <NUM> may extend substantially perpendicular to the sidewall <NUM>. The flexible duct <NUM> freely passes over the break <NUM> as the flexible duct <NUM> is threaded onto the ferrule <NUM>. However, if the flexible duct <NUM> attempts to unthread itself from the ferrule <NUM>, the break <NUM> snags and bites into the flexible sheet material <NUM> to resist unthreading of the flexible duct <NUM>. A second end of the discontinuous portion may include a ramped surface <NUM> extending at an angle from the sidewall <NUM> to the crest of the at least one thread <NUM>. The ramped surface <NUM> may in particular be angled to prevent snagging of the flexible sheet material <NUM> as the flexible duct <NUM> is threaded onto the ferrule <NUM> over the discontinuous portion. As shown in <FIG>, the at least one thread <NUM> may include multiple discontinuous sections to increase the resistance to unthreading of the flexible duct <NUM>.

While the connection between the flexible duct <NUM> and the ferrule <NUM> has been described herein with reference to a flexible duct <NUM> including the helix structure <NUM>, it is to be understood that the ferrule <NUM> may also be connected to a flexible duct <NUM> lacking a helix structure <NUM>. In such embodiments, the at least one thread <NUM> of the ferrule <NUM> engages the flexible sheet material <NUM> to radially expand the flexible sheet material <NUM>. Circumferential tension thereby generated in the flexible sheet material <NUM>, along with friction between the flexible sheet material <NUM> and the sidewall <NUM>, secure the flexible duct to the ferrule <NUM>.

Referring now to <FIG>, <FIG>, and <FIG>, the fitting assembly <NUM> may include a fitting <NUM> connected to the ferrule <NUM>. The fitting <NUM> may be, or may include, any type of component of an HVAC system such as an elbow, a tee, a manifold takeoff, a coupling, a terminal boot, a cap, a plug, a union, or a flange. As shown in <FIG>, <FIG>, and <FIG>, the fitting <NUM> may define one or more recesses <NUM> for receiving one or more tabs <NUM> formed on and/or extending from the second end <NUM> of the ferrule <NUM>. In some embodiments, each of the one or more recesses <NUM> may be in the form of a through hole extending entirely through a sidewall of the ferrule <NUM>. In some embodiments each of the one or more recesses <NUM> may be in the form of a blind hole extending only partially through the sidewall of the ferrule <NUM>.

Each tab <NUM> of the ferrule <NUM> may be radially deflectable and may include a projection or tooth <NUM> that snaps into one of the recesses <NUM> of the fitting. In some embodiments, the one or more tabs <NUM> may be evenly spaced around the circumference of the ferrule <NUM>, while the one or more recesses <NUM> may be evenly spaced around the circumference of the fitting <NUM> such that each tab <NUM> aligns with one of the recesses <NUM>. The snap fit between the fitting <NUM> and the ferrule <NUM> allows the connection of the fitting <NUM> and the ferrule <NUM> to be performed by hand so that the user can rapidly and securely assemble the fitting assembly <NUM> without the need for specialized tools or advanced training.

Additional details of the one or more tabs <NUM> of the ferrule are shown with reference to <FIG>. The tooth <NUM> may extend radially inward from an inner surface <NUM> of the ferrule <NUM>. In some embodiments, the tooth <NUM> may include one or more ramped surfaces <NUM> sloping in a circumferential direction of the ferrule <NUM> that assist in assembly and disassembly of the fitting assembly <NUM>. During assembly, the one or more ramped surfaces <NUM> may help guide the tooth <NUM> into alignment with the corresponding recess <NUM> as the ramped surface <NUM> engages an edge <NUM> of the recess <NUM>. During disassembly, the user may rotate the ferrule <NUM> relative to the fitting <NUM>, causing the ramped surface <NUM> to slide over an edge <NUM> of the recess <NUM> and thereby deflect the tab <NUM> radially outward. If sufficient rotational force is applied, the tooth <NUM> may be entirely dislodged from the recess <NUM>, allowing the user to separate the fitting <NUM> from the ferrule <NUM> by pulling along the longitudinal axis LD.

Each of the one or more recesses <NUM> may have a width extending in the circumferential direction of the fitting <NUM> equal to or greater than a width of the tooth <NUM> of the corresponding tab <NUM>. If the width of the recess <NUM> is substantially equal to width of the tooth <NUM>, rotation of the fitting <NUM> relative to the ferrule <NUM> is prevented by abutment of the tooth <NUM> against the edges of the recess <NUM>. However, if a sufficient rotational force is applied to the fitting <NUM> and/or the ferrule <NUM>, the ramped surface <NUM> may slide over the edge <NUM> of the recess <NUM> and become dislodged, as described herein. Therefore, the angle of slope of the ramped surfaces <NUM> may be selected such that rotational force required to dislodge the tooth <NUM> from the recess <NUM> is not less than incidental forces that might be experienced by ferrule <NUM> and fitting <NUM> in service, but is not greater than a force that can readily be applied by the user (either manually or with the assistance of tools) when intentionally dislodging the tooth <NUM> from the recess <NUM>.

In some embodiments, the width of the recess <NUM> may be greater than the width of the tooth <NUM>, such that the ferrule <NUM> may be rotated by some amount less than <NUM>° relative to the fitting <NUM> before the tooth <NUM> abuts the edge <NUM> of the recess <NUM>. As such, there may be controlled and limited rotational freedom between the ferrule <NUM> and the fitting <NUM>.

In the embodiments shown in the accompanying drawings, the one or more tabs <NUM> are disposed on the ferrule <NUM> and the one or more recesses <NUM> are defined in the fitting <NUM>. In other embodiments, the one or more tabs <NUM> may be disposed on the fitting <NUM> and the one or more recesses <NUM> may be defined in the ferrule <NUM>. In some embodiments, the tooth <NUM> of each of the one or more tabs <NUM> may extend radially outward, rather than radially inward as shown in the drawings. In such embodiments, the one or more recesses <NUM> may be provided on an inner surface of the fitting <NUM> or the ferrule <NUM> to receive the outwardly projecting tooth <NUM>.

In the embodiments shown in the accompanying drawings, the ramped surfaces <NUM> are provided on the tooth <NUM> of each tab <NUM> and the edges <NUM> are defined at the perimeter of each recess <NUM> to facilitate assembly and disassembly of the fitting assembly <NUM>. In other embodiments, the one or more recesses <NUM> may include ramped surfaces which engage an edge of the tooth <NUM> to facilitate assembly and disassembly of the fitting assembly <NUM>.

With the fitting <NUM> and the ferrule <NUM> connected via the engagement of the one or more tabs <NUM> with the one or more recesses <NUM>, the interface between the ferrule <NUM> and the fitting <NUM> may form an air tight connection. With reference to <FIG>, <FIG>, and <FIG>, a portion of the inner surface <NUM> of the ferrule <NUM> may be conically shaped to engage a conically-shaped outer surface <NUM> of the fitting <NUM>. The conical portions of the inner surface <NUM> of the ferrule <NUM> and the outer surface <NUM> of the fitting <NUM> may have a taper of, for example, between <NUM>° and <NUM>°. In other embodiments, the inner surface <NUM> of the ferrule <NUM> and the outer surface <NUM> of the fitting <NUM> may be spherically shaped. The inner surface <NUM> of the ferrule <NUM> and the outer surface <NUM> of the fitting <NUM> may engage with an interference fit when the ferrule <NUM> and the fitting <NUM> are assembled to create the air tight seal.

As the interface between the ferrule <NUM> and the fitting <NUM> may be air tight, the need for additional sealing components such as clams, fasteners, gaskets, mastics, and/or sealants may be eliminated. In other embodiments, one or more of such sealing components may be applied to the interface between the ferrule <NUM> and the fitting <NUM>.

With continued reference to <FIG>, <FIG>, and <FIG>, in some embodiments, a depression <NUM> may extend around the circumference of the ferrule <NUM>. The depression <NUM> may have a diameter less than the major diameter Dmaj of the sidewall <NUM>. The depression <NUM> may be configured to receive the terminal end <NUM> of the flexible duct <NUM> as the flexible duct is threaded onto the at least one thread <NUM>. Once the terminal end <NUM> of the flexible duct <NUM> is received in the depression <NUM>, a clamp <NUM> may be fastened around the depression <NUM> to secures the flexible duct <NUM> to the ferrule <NUM>. The clamp <NUM> may be, for example, a cable clamp, hose clamp, zip tie, cable tie, or the like. The clamp <NUM> prevents inadvertent unthreading to the flexible duct <NUM> from the ferrule <NUM>.

With continued reference to <FIG>, <FIG>, and <FIG>, in some embodiments, the ferrule <NUM> may include a grip <NUM> for assisting the user in grasping the ferrule <NUM> during connection of the ferrule <NUM> to the flexible duct <NUM>, and during assembly and disassembly of the fitting assembly <NUM>. The grip <NUM> may include, in some embodiments, a plurality of ribs extending radially from the ferrule <NUM>. In some embodiments the grip <NUM> may include a plurality of tabs extending from opposing sides of the ferrule <NUM>, similar to a wing nut. The grip <NUM> may be configured to prevent slippage of the ferrule <NUM> in the user's hand when a rotational force, such as that applied to disconnect the ferrule <NUM> from the fitting <NUM>, is imparted to the ferrule <NUM>.

Referring again to <FIG>, the components of the ductwork assembly <NUM>, including the flexible duct <NUM>, the fitting <NUM>, and the ferrule <NUM>, may be manufactured from materials that are generally heat insulators to maintain the temperature of air conveyed through the ductwork assembly <NUM>. The helix structure <NUM> of the flexible duct <NUM> may be manufactured from steel or a similar resilient, shape memory material capable of supporting the shape of the flexible sheet material <NUM> and able to withstand deformation as the flexible duct <NUM> is connected to the ferrule <NUM>. The flexible sheet material <NUM> may be manufactured from a resilient material, such as a thin-wall polyvinyl chloride (PVC) or polyurethane foam, so that the flexible sheet material <NUM> can deform against the at least one thread <NUM> and the sidewall of the ferrule <NUM>. The flexible sheet material <NUM> may have a thickness, for example, of less than <NUM> inches or of less than <NUM> inches. The fitting <NUM> and the ferrule <NUM> may be manufactured from one or more materials including but not limited to: plastic, such as PVC or acrylonitrile butadiene styrene (ABS); composite materials such as a fiber-reinforced polymer; metal; or non-combustible material.

Sizing of the components of the ductwork assembly <NUM> may be selected based on the desired air flow rate within the ductwork assembly <NUM>. The flexible duct <NUM> is typically manufactured in a variety of nominal sizes that dictate the sizing of the fitting <NUM> and the ferrule <NUM>. In particular, the major and minor diameters Dmaj, Dmin of the ferrule <NUM> may be based on the diameter of the flexible duct <NUM> to facilitate proper engagement of the ferrule <NUM> and the flexible duct <NUM>, as discussed herein with reference to <FIG>. In some embodiments, the major diameter Dmaj may be in a range of <NUM> percent to <NUM> percent greater than the inner diameter of the flexible duct <NUM>. In some embodiments, the minor diameter Dmin may be in a range of <NUM> percent to <NUM> percent less than the inner diameter of the flexible duct <NUM>. In some embodiments, the taper of the sidewall <NUM> between the major and minor diameters Dmaj, Dmin of the ferrule <NUM> may be in the range of <NUM> to <NUM> degrees. In some embodiments, the maximum height of the at least one thread <NUM> of the ferrule <NUM> may be in the range of <NUM> millimeters (mm) and <NUM>. In some embodiments, the length of the sidewall <NUM> between the major and minor diameters Dmaj, Dmin of the ferrule <NUM> may be in the range of <NUM> to <NUM>. In some embodiments, the pitch PF of the at least one thread <NUM> of the ferrule <NUM> may be in the range of <NUM> to <NUM>. It is to be understood that the foregoing values and ranges of values for sizing the components of the ductwork assembly <NUM> are presented only for exemplary purposes and are not to be construed as limiting.

Claim 1:
A fitting assembly (<NUM>) for connection to a flexible duct (<NUM>), the fitting assembly (<NUM>) comprising:
a ferrule (<NUM>) configured for insertion into an open end of the flexible duct (<NUM>), the ferrule (<NUM>) comprising:
a sidewall (<NUM>) defining a minor diameter (Dmin) and a major diameter (Dmaj) spaced apart from the minor diameter (Dmin); and
a ferrule thread (<NUM>) extending radially outward from the sidewall (<NUM>);
a fitting (<NUM>) removably connected to the ferrule (<NUM>),
wherein the minor diameter (Dmin) is less than or equal to an inner diameter of the flexible duct (<NUM>) with the flexible duct (<NUM>) in an untensioned state,
wherein the major diameter (Dmaj) is greater than the inner diameter of the flexible duct (<NUM>) with the flexible duct (<NUM>) fully elongated,
wherein one of the fitting (<NUM>) and the ferrule (<NUM>) defines a recess (<NUM>),
wherein the other of the fitting (<NUM>) and the ferrule (<NUM>) comprises a tab (<NUM>) configured to extend into the recess (<NUM>),
wherein one of the recess (<NUM>) and the tab (<NUM>) comprises an edge (<NUM>), characterized in that the other of the recess (<NUM>) and the tab (<NUM>) comprises a ramped surface (<NUM>) extending in a circumferential direction of the ferrule (<NUM>), such that rotation of the ferrule (<NUM>) relative to the fitting (<NUM>) causes the ramped surface (<NUM>) to engage the edge (<NUM>), thereby radially deflecting the tab (<NUM>) and disengaging the tab (<NUM>) from the recess (<NUM>).