Pipes and tubular conduits – Longitudinally seamed – With tongue in slot
Reexamination Certificate
1999-03-16
2001-08-14
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
Longitudinally seamed
With tongue in slot
C138S162000, C138S156000
Reexamination Certificate
active
06273145
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to heating, ventilation and air conditioning (HVAC) duct systems and, more specifically, it relates to a folded and hinged plastic connector for use with HVAC duct work.
HVAC systems are designed to provide control of space temperature, humidity, air contamination, differential pressurization, and air motion. These distribution systems use a network of ducts to deliver the heated and/or cooled air to the various rooms and spaces within the building structure. These air ducts are usually rectangular or round passages and are made from a variety of materials. When these ducts are accurately sized and the duct system is correctly designed, the air will be delivered to the rooms and spaces with a minimum of resistance.
Of the many HVAC systems currently available, galvanized sheet steel duct systems are among the most widely used. These systems generally consist of an air heating and/or refrigeration unit, straight sections of duct, and multiple types of fabricated fittings and connections. From these fittings and connections, the straight sections of duct are connected to each other and to openings or vents in the rooms and spaces of the building structure. Currently, the duct and the connections and fittings are fabricated primarily by experienced sheet metal workers.
In recent times, several issues have developed with the design of the connections and fittings used in HVAC systems. First, the connections and fittings are difficult to store, handle, and transport without damaging them. In addition, due to their current shape and design, they require a large quantity of space per unit to store and transport. These problems cause excessive scrap and increased inventory holding and transportation costs for the distributor and customers.
In order to solve some of these problems, at least with duct-to-register connections, it has been proposed to fabricate sheet metal duct-to-register connectors which can be blanked and partly folded at the factory, shipped stacked compactly together, and bent into final form at the site of installation. Thus, in McGann U.S. Pat. No. 3,606,404 there is disclosed a sheet metal strip, foldable to a rectangular cross-section to fit within a register aperture, which has a margin along one of its longer edges to bend an inward shoulder, and bendable tabs extending therefrom. The shoulder seats against the outer margin of a duct opening smaller than the room surface aperture for the register. But, metal stamping of such parts requires expensive dies and equipment and the parts still must be finally formed at the site. Even then, the duct-to-register connectors of McGann are designed for use only with wood floor joists.
Another issue with the current design of the connections and fittings used in HVAC systems is the excess labor and materials cost that is often required when installing them into cement slab foundations. Without consulting all of the building codes and standards for all of the locations in which this product may be used, general installation practices demand that the duct must be painted and wrapped in plastic bags to prevent rust and corrosion when placed in a cement slab foundation. Accordingly, it would be desirable to have plastic duct work or at least plastic duct connectors.
Of course, in other fields plastic ducts are known. For example, Corsi et al in U.S. Pat. No. 4,942,271, discloses a plastic duct assembly for enclosing conduits, cables, wires, lines and the like, comprising a base having a generally U-shaped cross section along its longitudinal axis. The base includes a generally planar central portion with first and second legs extending substantially perpendicular thereto. The cover includes an intermediate portion having third and fourth legs extending substantially perpendicular thereto. The cover is pivotally and releasably coupled to the base at one end and releasably coupled to the base at the other end. The pivotal and releasable coupling is made up and released via a snap fit resulting from forces exerted substantially perpendicular to the longitudinal axes of the cover and the base. But, the Corsi et al plastic duct is not designed for use with HVAC systems. In addition, it cannot be stored and transported in the unfolded, flat position and cannot be stacked in that position to save space. It is, therefore, as awkward to handle as much of the prior art duct work.
Thus, most prior art fittings and connections are often very awkward to use and handle. The current design allows very little flexibility in assembly which in some cases increases labor and scrap cost. They also contain sharp edges and corners which occasionally cause cuts and abrasions which increase labor cost and put the laborers' safety at an unneeded risk.
Accordingly, the need still exists for inexpensive devices that provide ease of assembly and opportunities for cost reduction in labor, scrap, and inventory holding costs currently associated with HVAC duct systems.
SUMMARY OF THE INVENTION
That need is met by the present invention which provides a plastic duct connector for use in HVAC systems which effectively eases assembly, access, and reduced safety risks for installation and maintenance personnel. Further, the plastic duct connector of the present invention provides an inexpensive alternative to rigid duct fittings and connections.
The plastic duct connector of the present invention is of the type which has one end capable of being connected, by screws or otherwise, to HVAC duct work and at the other end is capable of being connected to a register opening or other HVAC duct work.
For example, it may be a register boot, a duct or duct fitting, a twist-in collar, a reducer or increaser, a cover or collar, a wyer or tee, a flex fitting, a wall stack or stack fitting or an ovals pipe or pipe fitting.
A main feature of the present invention is that a plastic form is produced, such as by injection molding, so as to have two or more sections and a hinged joint between each of the sections about which the sections may be pivoted to fold and assemble the plastic duct connector. For example, the hinged joint may be formed during the molding process such as by reducing the thickness of the plastic form at the folding point to around 0.005 to 0.12 inch so as to form a living hinge, which is also known as a pinless plastic utility hinge. Other types of hinge structures may also be used. Among the other hinge types which may be used are continuous hinge, geared hinge, lift-off multipurpose hinge, surface hinge, utility hinge, cabinet hinge, back flap hinge, plastic butt hinge, bifold-door hinge, and strap hinge structures.
The body portion of the plastic forrri is, then, preferably 0.06 to 0.2 inch thick. The plastic used to mold the plastic form is preferably polypropylene. Other plastics that will meet U/L requirements may also be used. Among the other types of plastics that may be used are acrylonitrile butadiene styrene, acrylic, polyamide, polycarbonate, polyethylene, polystyrene, polyvinyl chloride, and polyester resins.
Fastening devices are located at the edges of the body portion of the plastic form for holding the sections together after being folded and joined. Preferably the fastening devices are cantilever self-locking snaps having snap tabs/locking tabs formed during the molding process. Other types of fastening devices may also be used. Among the other types of fastening devices that may be used are positive-locking hook latch, snap slide latch, spring clip holder, plastic snap rivets, plastic removable rivets, push-in panel rivets, keyhole panel rivets, panel rivets, ratchet rivets, and tree rivets fasteners. Once the plastic form is in the desired location, the sections are then folded together completely until all the fastening devices have engaged.
Because the duct connector of the present invention is plastic, it has a number of advantages over sheet metal ones. That is, it does not have sharp edges, it is lightweight, it is easily manufactured in various sizes and shapes at low
Brinson Patrick
Killworth, Gottman Hagan & Schaeff, L.L.P.
Paramount Concepts Ltd.
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