Patent Application
20070220732
The present invention relates generally to vents and ducts for gas transport and, more particularly, to ducts of the type commonly installed as exhaust transition ducts for household and commercial clothes dryers and as air ducts in heating, ventilation, and air conditioning (HVAC) systems.
Air ducts for ventilation systems are well known. They are typically used to direct air flow for heating and air conditioning systems. Another common application is for the exhaust vent of clothes dryers.
A very typical and common exhaust vent for clothes dryers is fabricated of a resilient wire helix which is covered with vinyl tubing, which lacks structural integrity and is generally not flame resistant or with aluminum tubing, which lacks structural integrity. The lack of structural integrity typically results in sagging and crinking of the duct. Ducts of these types also tend, over time, to become lined with lint from the clothes dried in the dryer, posing a fire hazard. According to the Consumer Products Safety Commission, there are over 15,000 fires annually associated with clothes dryers, causing deaths and injuries and some $90 million in damages. It is generally recommended by clothes dryer manufacturers not to use vinyl ducts such as these for dryer exhaust transition ducts.
Representative of the prior art in ventilation systems is U.S. Pat. No. 5,281,187, included herein by reference, to Whitney for a “Unitary Vent and Duct Assembly” which discloses a “semi-rigid flexible duct” for a ventilation system installed with a suspended ceiling structure. The duct taught in this patent is actually a solid aluminum tube which is corrugated or “accordion-folded” so that it can be compressed or compacted for storage or shipping. The corrugated aluminum tube duct taught therein, is meant to be coupled to a duct assembly of which it is an integral part, which is intended only for installation within a framed section of a suspended or dropped ceiling. However, once such a tube has been compressed and then re-extended for installation, it may not be likely to maintain its rigidity, depending on the thickness of the aluminum. A tube of this type that will maintain its rigidity, by virtue of its being fabricated of solid metal, will be heavy and expensive and can be unwieldy to install. The corrugated aluminum, when extended after compression, will have significant ridges and other obtrusive topographical features along its interior due to the corrugations, which will cause frictional resistance to the air flow within, a further disadvantage.
Corrugated aluminum is also employed for the exhaust vent of clothes dryers, as, for example, in U.S. Pat. Nos. 5,121,948, 5,133,579, and 5,145,217, which also solve the above-described problem of insufficient rigidity by using totally rigid segments. Even though the aluminum tubing itself is obviously fire resistant, the ridges and other internal topographical features similar to those mentioned hereinabove with respect to the Whitney patent, also cause fictional resistance to the air flow within, permitting accumulation of lint, which, as stated hereinabove, presents a fire hazard.
U.S. Pat. No. 5,526,849, included herein by reference, to Gray for a “Flexible Duct” discloses a duct and a method for manufacture thereof. The duct disclosed therein is formed of plastic tapes wound on a rotating mandrel with a wire resilient helix and a yarn helix therebetween. The duct so produced, while flame resistant, has rigidity limited to that provided by the wire helix. The additional yarn helix complicates the manufacturing process and adds to the internal topographical features of the duct, increasing friction and the possibility of lint accumulation therein, as described above.
The present invention seeks to provide a flexible duct for a ventilation system, and particularly for clothes dryer exhaust, that is fire resistant and that is lighter in weight and less expensive than those used in the prior art, while maintaining rigidity and structural integrity, even after having been compressed to a compacted configuration for shipping and storage and then re-extended for installation. Further, the duct should have minimal internal topographical features or structure, even after having been compressed to a compacted configuration for shipping and storage and then re-extended for installation. The present invention further seeks to provide a method for manufacturing such a duct that is simple, fast, and efficient.
There is thus provided, a semi-rigid, flexible, duct for gas transport and in particular, to serve as a clothes dryer exhaust transition duct, having an axis, including a pair of coaxial sleeves, including an inner sleeve and an outer sleeve disposed parallel to and about the inner sleeve, and a resilient helical element disposed between them;
When a predetermined length of the duct is in the extended configuration and is disposed horizontally and supported at a first end thereof, the duct is fabricated to bend under the influence of gravitational force such that a second unsupported end thereof is lower than the first supported end by no more than a predetermined percentage of the predetermined length. Further, when a predetermined length of the duct is in the extended configuration and is disposed horizontally and supported at both ends thereof, the duct is fabricated to bend under the influence of gravitational force such that the central portion thereof is also lower than the level of the supported ends by no more than a predetermined percentage of the predetermined length, which, for a 2 meter length of a duct with a diameter of approximately 10 centimeters, will be less than 1 centimeter for an extended duct that was not compacted and less than 5 centimeters for a duct that was extended from the compacted configuration. Additionally, when the duct is in the extended configuration after having been compressed to the compacted configuration, the inward-facing surface of the first layer having metallic properties of the inner sleeve is substantially smooth and featureless except for the helical corrugations.
Further, both the inner sleeve and the outer sleeve include a first layer having metallic properties and a second, plastic layer, forming thereby, respectively, an inner two-layer laminate and an outer two-layer laminate, which are fabricated of fire-resistant and puncture-resistant materials. In all of the two-layer laminates, the layers are bonded together with a fire-retardant adhesive and the inner two-layer laminate is also bonded to the outer two-layer laminate with a fire-retardant adhesive. Additionally, the first layers having metallic properties of the inner two-layer laminate and the outer two-layer laminate are fabricated of aluminum ribbon of predetermined thicknesses and the second, plastic layers of the inner two-layer laminate and the outer two-layer laminate are fabricated of polyester ribbon of predetermined thicknesses, respectively bonded together to form thereby, respectively, an inner two-layer laminated tape of predetermined thickness and an outer two-layer laminated tape of predetermined thickness, and wherein the inner two-layer laminate is an inner helical wrapping with a predetermined overlap of the inner two-layer laminated tape and the outer two-layer laminate is an outer helical wrapping with a predetermined overlap of the outer two-layer laminated tape. Further, in the inner sleeve, the second plastic layer is disposed parallel to and about the first layer having metallic properties and in the outer sleeve, the first layer having metallic properties is disposed parallel to and about the second plastic layer. The first layer having metallic properties of the inner two-layer laminate is fabricated of aluminum ribbon of a thickness in the range of 6 to 12 microns, and the first layer having metallic properties of the outer two-layer laminate is fabricated of aluminum ribbon of a thickness in the range of 24 to 35 microns. The second plastic layers of both the outer and inner two-layer laminates are fabricated of polyester ribbon of a thickness in the range of 10 to 14 microns.
Additionally, the resilient helical element is fabricated of a metal having spring-like resilience, such as a coiled bronze-coated steel wire of a diameter in the range of 0.9 to 1.3 millimeters.
Further, in accordance with a preferred embodiment of the invention, the resilient helical element is aligned with the inner helical wrapping so that the coiled bronze-coated steel wire is approximately centered over the overlap of the inner helical wrapping of the inner two-layer laminated tape and the outer helical wrapping of the outer two-layer laminated tape is aligned with the resilient helical element so that the overlap of the outer helical wrapping of the outer two-layer laminated tape is approximately centered over the spaces between the wires of the coiled bronze-coated steel wire of the resilient helical element.
In accordance with a further embodiment of the invention, the duct also includes an insulating sheath fabricated of fiberglass, disposed parallel to and about the outer sleeve, and an enclosing jacket disposed parallel thereto and thereabout. The enclosing jacket is a multi-layer jacket including a tubular, plastic inner wrapping and a two-layer laminate outer wrapping, including a plastic inner layer and an outer layer having metallic properties, bonded together with a fire-retardant adhesive, disposed parallel and about the tubular, plastic inner wrapping and bonded thereto with a fire-retardant adhesive. The plastic inner wrapping is fabricated of polyester ribbon of predetermined thickness, and the plastic inner layer of the two-layer laminate outer wrapping is fabricated of polyester ribbon of predetermined thickness and the outer layer having metallic properties of the two-layer laminate outer wrapping is fabricated of aluminum ribbon of predetermined thickness. The insulating sheath is fabricated of fiberglass of a thickness in the range of 25 to 50 millimeters. The plastic inner wrapping is fabricated of polyester ribbon of a thickness in the range of 10 to 14 microns. The plastic inner layer of the two-layer laminate outer wrapping is fabricated of polyester ribbon of a thickness in the range of 10 to 14 microns, and the outer layer having metallic properties of the two-layer laminate outer wrapping is fabricated of aluminum ribbon of a thickness in the range of 6 to 9 microns.
There is further provided, in accordance with the present invention, a method for manufacturing a semi-rigid, flexible, duct of a preselected diameter for gas transport, including the steps of:
Additionally, the step b) of combining a first aluminum ribbon includes the sub-step of applying a fire-retardant adhesive between the first aluminum ribbon and the first polyester ribbon to bond them together; and the step of c) combining a second aluminum ribbon includes the sub-step of applying a fire-retardant adhesive between the second aluminum ribbon and the second polyester ribbon to bond them together. Further, the step of b) combining a first aluminum ribbon further includes the sub-step of coating the polyester face of the first two-layer laminated continuous tape with a fire-retardant adhesive; the step c) of combining a second aluminum ribbon further includes the sub-step of coating the polyester face of the second two-layer laminated continuous tape with a fire-retardant adhesive; and in the step d) of helically wrapping the second two-layer laminated continuous tape, the outer two-layer sleeve is bonded to the inner two-layer sleeve with the bronze-coated steel wire helically coiled therebetween.
Additionally in accordance with the method of the present invention, the step e) of helically coiling a bronze-coated steel wire includes the sub-step of aligning the coiled wire with the overlap in the wrapping of the inner two-layer sleeve so that the coiled wire is approximately centered over the overlap in the wrapping of the inner two-layer sleeve, and the step f) of helically wrapping the second continuous two-layer laminated tape includes the sub-step of aligning the wrapping of the second continuous two-layer laminated tape so that the overlap in the wrapping of the outer two-layer sleeve is approximately centered over the spaces between the coils of wire.
Further in accordance with the method of the present invention, the steps d), e), and f) of helically wrapping the first two-layer laminated continuous tape, helically coiling the bronze-coated steel wire, and helically wrapping the second two-layer laminated continuous tape are performed by rotating the mandrel as the first two-layer laminated continuous tape, the bronze-coated steel wire, and the second two-layer laminated continuous tape are respectively deposited thereupon; and the steps d), e), and f) of helically wrapping the first two-layer laminated continuous tape, helically coiling the bronze-coated steel wire, and helically wrapping the second two-layer laminated continuous tape are performed continuously and simultaneously with predetermined phase differences, with respect to the rotation of the mandrel, therebetween. Namely, the steps d) and e) of helically wrapping the first two-layer laminated continuous tape and helically coiling the bronze-coated steel wire are performed continuously and simultaneously with a phase difference of 360 degrees, with respect to the rotation of the mandrel, therebetween; and the steps e) and f) of coiling the bronze-coated steel wire and helically wrapping the second two-layer laminated continuous tape are performed continuously and simultaneously with a phase difference of 120 degrees, with respect to the rotation of the mandrel, therebetween.
In accordance with an additional embodiment of the present invention, the method further includes, after the step f) of helically wrapping the second two-layer laminated tape, the steps of:
1) providing a mandrel of preselected diameter for fabricating the enclosing jacket therearound;
The sub-step 2) of combining includes the sub-sub-step of applying a fire-retardant adhesive between the polyester ribbon and the aluminum ribbon to bond them together, and the sub-step 3) of helically wrapping a polyester ribbon includes the sub-sub-step of coating the outer face of the inner plastic sleeve with a fire-retardant adhesive to bond it to the two-layer laminated tape.
Additionally, the sub-steps 3) and 4) of helically wrapping a polyester ribbon and helically wrapping the two-layer laminated tape are performed by rotating the mandrel as the polyester ribbon and the two-layer laminated tape are respectively deposited thereupon. Further, the sub-steps 3) and 4) of helically wrapping a polyester ribbon and helically wrapping the two-layer laminated tape are performed continuously and simultaneously with a predetermined phase difference, namely, of 360 degrees, with respect to the rotation of the mandrel, therebetween.
The present invention will be more fully understood and appreciated from the following detailed description, taken in conjunction with the drawings, in which:
Referring now to the drawings, there are shown, in
Polyester ribbon layers 224 and 234 are both heat resistant and fire retardant and further are made thick enough to contribute to the rigidity and structural integrity of duct 100 together with aluminum ribbon layers 222 and 232, which, being metallic, are fireproof as well. The adhesive employed in adhesive layers 240, 260, and 280 is also heat resistant and fire retardant. It should be noted that polyester ribbon layers 224 and 234 are also puncture resistant, which is a further advantage of the duct 100 of the present invention.
Duct 100 is manufactured fully extended by a continuous process, further described hereinbelow, and is then cut to a desired length. The corrugations 160 imparted thereto by helical wire 250 allow duct 100 to be axially compressed into a compact configuration convenient for storage or shipping. When duct 100 is compressed, as shown in
A particular advantage of the unique, multilayered construction of the present invention is that duct 100 maintains its rigidity and structural integrity and functions like a totally rigid duct even after having been compressed to its compact configuration and re-extended to its original length. Referring now to
Another advantage of the unique multilayered construction of the present invention is that when it is fully extended after compression, the inward-facing surface of the aluminum layer 222 of the inner sleeve 220 is substantially smooth and featureless except for the helical corrugations imparted by wire helix 250. This reduces frictional resistance to air flow within the duct, and, for clothes dryer exhaust transition ducts, significantly impedes the accumulation of lint inside the duct, thereby greatly reducing the fire hazard cited hereinabove with respect to the prior art.
Referring again to
Referring now to
In a preferred embodiment of the present invention, insulating layer 470 and enclosing jacket 490 of duct 400 have the following dimensions. Depending on the application, insulating layer 470 typically may be either 25 or 50 millimeters in thickness. The wrapping of polyester ribbon 484 is 12 microns thick. The two-layer laminated tape of the outer helical wrapping has an inner polyester ribbon layer 494 that is 12 microns thick and an outer aluminum ribbon layer 492 that is 7 microns thick, so that, with the adhesive 495, outer helical wrapping has a thickness of 21 microns. It should be noted that the above-mentioned dimensions are typical and are exemplary of a preferred embodiment of the present invention, and that the present invention is not limited thereto.
Enclosing jacket 490 is manufactured by a continuous process, similar to that of duct 100, and is then cut to a desired length. Duct 400 is assembled from an insulating layer 470 cut to the desired length and an enclosing jacket 490 cut to the desired length, which are drawn onto a segment of uninsulated duct, similar to duct 100, cut to the desired length.
Referring now to
The advantageous properties of the duct of the present invention result both from its unique construction described hereinabove and from the method of manufacture thereof. Referring now to
Referring now to
Returning now to
For the insulated duct 400 of
To produce insulated duct 400, a piece of continuously produced uninsulated duct 700 is cut to the desired length, and a piece of continuously produced enclosing jacket 490 is cut to the desired length. As shown schematically in
It will further be appreciated by persons skilled in the art that the scope of the present invention is not limited by what has been specifically shown and described hereinabove, merely by way of example. Rather, the scope of the present invention is defined solely by the claims, which follow.
