Supports – Pipe or cable – Suspended
Reexamination Certificate
2003-05-20
2004-04-13
Ramirez, Ramon O. (Department: 3632)
Supports
Pipe or cable
Suspended
C248S339000
Reexamination Certificate
active
06719247
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a hanger for suspending pipes from a support structure, and in particular to a J-shaped hanger for mounting flexible conduit.
The heating, ventilation and air conditioning (HVAC) system is an important part of many dwelling structures. Such a system can be used to heat, cool, purify or otherwise condition air for use by people inside the dwellings. In most HVAC systems, especially those for use in private residential structures, such as houses and apartments, the air is moved from its source to its destination through pipes and related air-handing ductwork, or conduit. The conduit is typically mounted in a relatively unobtrusive location, such as underneath a floor, or from a joist or similar overhead support, using hangers or brackets to secure the conduit to the support structure. In one configuration, the hanger includes a hook or clamp portion to receive the conduit, and a mounting portion opposite the hook or clamp portion for attachment to the support structure. Another configuration involves the use of a simple strap (such as woven plastic) that is cut into appropriate lengths such that the strap could be looped around the conduit with the strap ends brought together and secured to the joist by piercing the ends and the joist with a nail, screw or similar fastener.
Flexible conduit, also called flexible duct, has often been used in HVAC systems in place of traditional rigid pipe or fabricated sheet metal due to its safe and inexpensive manufacture, storage and installation. During the installation of flexible duct in an HVAC system, personnel would typically use a simple strap to mount the duct to a joist. This operation could be unwieldy, as the installer would have to provide temporary support of the duct while concurrently attempting to nail or screw in the strap. This operation is exacerbated by the confined nature of the installation location. Such installation is also potentially dangerous, as the installer is often in an elevated space, where the risk of injury due to falling is significant.
There have been attempts in the art to simplify the steps of installing air-handling conduit through improved hangers. However, most of such activity has focused solely on hangers for rigid conduit. For example, U.S. Pat. No. 4,407,478, issued to Hodges on Oct. 4, 1983, discloses a pipe hanger including a stem portion and a curved portion. The stem portion includes holes to permit attachment of the hanger to a support structure, such as a joist. The curved portion defines an arc into which the pipe is accepted, and is configured such that the pipe can be snap-fit therein due to the presence of a protruding locking lobe. The arc of the curved portion subtends an angle in excess of 180 degrees, so that the remote end of the curved portion must be temporarily flexed outward, thereby allowing the pipe to be secured inside.
Unfortunately, such a configuration does not work well with flexible duct, as the snap-fit can cause crimping of the duct. This crimping can adversely effect the flow and quality of air passing through the duct. Similar problems arise when straps are used to support flexible duct, as the weight of the duct is often sufficient to cause crimping at the location of limited contact surface area due to the strap. Moreover, in either of the above cases, if the duct is subject to movement (due, for example, to vibration), the crimped spot can become weakened, leading to a breech in the duct, with concomitant reduction in airflow to the intended location. Other related hanger devices use a latch-based mechanism to keep the duct secured within the curved region of the hanger. Additional problems are encountered when the duct needs to be moved for servicing or replacement. In the snap-fit and latched hanger devices, a separate step of unsecuring the duct from the hanger must be undertaken prior to duct removal. As with the installation steps, this operation can be time-consuming and potentially hazardous. In the strap-based hanger devices, the procedure is even more unwieldy, as the person removing the duct must either rip the strap away from the fastener and the joist (possibly resulting in irreparable damage to the strap and necessitating an additional step upon reinstallation), or take the additional time to remove the fastener prior to removing the duct. All of the above devices and methods result in significant increases in the cost and complexity of installed HVAC ductwork.
Accordingly, what is needed is a hanger that will permit the simple support and attachment of flexible duct without unduly impeding the flow of air therein or damaging the duct wall. What is additionally needed is a hanger that will reduce the cost, complexity and risk of installing flexible duct.
BRIEF SUMMARY OF THE INVENTION
This need is met by the present invention, where a hanger for supporting flexible duct is disclosed. According to a first aspect of the invention, a hanger for mounting a flexible duct to a support structure is disclosed. The hanger is defined by a substantially elongate body comprising a proximal end coupled to a distal end. The proximal end is configured to engage the support structure, while the distal end terminates in a cradle. The cradle includes a near end defining a transition between the cradle and the distal end, and a remote end opposite the near end such that together they define a duct insertion gap between them. The duct insertion gap is greater than the diameter of the flexible duct such that the duct can be freely seated in the cradle. As used in the present context, a flexible duct is “freely seated” in a support (such as the aforementioned cradle) when it can be placed onto the support and permitted at least a limited range of motion in the axis from which it was inserted. Thus, in the present invention, if the duct is seated onto the cradle by placing the former onto the duct-engaging surface of the latter from a vertical direction, and no additional latches, snap-fits or other retaining devices are used to prevent the duct from being lifted out of the cradle along the same direction, then the duct is “freely seated” in the cradle, even if the fit within the cradle is fairly snug. A duct-engaging surface extends between the near and remote ends of the cradle, and is defined by an exaggerated contact area along at least a portion thereof. The extra surface provided by the exaggerated contact area can engage more of the outer wall surface of the flexible duct, thereby distributing the weight of the duct over a larger area, thereby reducing the likelihood of crimping and sagging. As used in the present context, an exaggerated component (such as the exaggerated contact area) is one that includes dimensions larger than that required to satisfy minimum load-bearing capabilities.
Optionally, the proximal end of the hanger includes a plurality of apertures configured to accept fasteners, thereby permitting the hanger to be secured to the support structure. The plurality of apertures can be spaced apart at selected distances along the body to accommodate joists (or similar support structure) of varying heights and angular positions. Moreover, the proximal end terminates in a mounting plate such that the plurality of apertures in the proximal end are disposed in the mounting plate. Additionally, the substantially elongate body of the hanger is of one-piece construction, and is preferably made from plastic, such as polypropylene. The hanger may also include at least one longitudinally disposed integral rib to provide increased rigidity. Moreover, the duct-engaging surface of the cradle is curvilinear in shape, and an arc defined by the curvilinear duct-engaging surface subtends an angle up to 180 degrees. The exaggerated contact area, which is used to inhibit sagging and crimping, is between two and four inches wide, and preferably approximately three inches wide at its widest point.
According to another aspect of the invention, a hanger for mounting a flexible duct to a support structure is d
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