This invention relates to the construction of a fabric innerduct which is placed in an underground conduit and which is adapted to receive a cable or other item therein. This invention also relates to the construction of a fabric pull tape used to pull a cable into the conduit. More particularly, this invention relates to such an innerduct or pull tape which is made of a system of fabric that reduces the friction of its insertion into the conduit. Moreover, the system of fabric makes the insertion of a cable into the innerduct easier while increasing the tensile strength of the innerduct.
Fabric innerducts, such as shown in U.S. Pat. No. 6,262,371, have been very successful in the communications industry. These innerducts are inserted into a conduit, which may extend for many miles underground, and they provide one or more compartments, or cells, into each of which a cable may be readily inserted. While such represents a significant improvement over their rigid innerduct predecessors, there is room for improvement in reducing the friction created when inserting the innerduct into the conduit and, in particular, when inserting a cable into a compartment of the innerduct.
These fabric innerducts must have the tensile strength to endure being pulled into a conduit, while at the same time provide as little frictional resistance as possible. To date these innerducts have been woven of a fabric material in such a way as to provide a compromise between high strength and low friction. Specifically, the fabric for these innerducts is typically woven with strands in the warp direction which are of a high tensile strength material and strands in the fill direction which are of a low friction material. Thus, some strength is lost, for the sake of low friction, and some friction is accepted for the sake of strength.
Pull tapes made of a fabric material and can be positioned in a compartment of an innerduct and thereafter utilized to pull a cable into the compartment. Like the innerduct, the pull tape must have the tensile strength required to pull the cable into the innerduct. However, prior art materials for such pull tapes have provided such tensile strength to the sacrifice of the ease of movement of the tape.
Thus, the need exists for an innerduct or pull tape which are made of a fabric which provides high tensile strength and at the same time low friction.
It is thus an object of one aspect of the present invention to provide a device to be introduced into a conduit, such as in the form of an innerduct or pull tape, which is made of two fabrics, one having a high tensile strength and the other having a low coefficient of friction.
It is an object of another aspect of the invention to provide a device, as above, whose outer surface is made of a material having a low coefficient of friction and which as an inner portion made of a material having high tensile strength.
These and other objects of the present invention, as well as the advantages thereof over existing prior art forms, which will become apparent from the description to follow, are accomplished by the improvements hereinafter described and claimed.
In general, a device to be inserted into a conduit includes a first material portion of a desired tensile strength and a second material portion having a desired coefficient of friction. The first and second material portions are positioned adjacent to each other.
In accordance with one particular aspect of the present invention, a device to be inserted into a conduit includes a first fabric material having a desired tensile strength and a second fabric material attached to the first fabric material and having a desired coefficient of friction.
According to another aspect of the present invention, a device to be inserted into a conduit includes a first fabric material having a desired coefficient of friction and a second fabric material attached to the first fabric material and having a desired tensile strength. A third fabric material is attached to the second fabric material and has a desired coefficient of friction.
In accordance with yet another aspect of the present invention, a device to be inserted into a conduit includes a plurality of strands of material. Each strand includes an inner core of a material having a desired tensile strength and another sheath of material around the core and having a desired coefficient of friction.
A preferred exemplary device in the form of an innerduct or pull tape according to the concepts of the present invention is shown by way of example in the accompanying drawings without attempting to show all the various forms and modifications in which the invention might be embodied, the invention being measured by the appended claims and not by the details of the specification.
An innerduct to be received in an underground conduct and made in accordance with the present invention is generally indicated by the numeral 10. Innerduct 10 is preferably made of a fabric material and can be of the type described in U.S. Pat. No. 6,262,371 to which reference is made for whatever details may be necessary for a full understanding of the present invention.
Innerduct 10 is shown as being made up of a plurality of cells, generally indicated by the numerals 11, 12 and 13. However, often times such innerducts may have only one cell or may have any number of a plurality of cells, three cells being shown herein. Cell 11 is made up of a fabric material 14 which is attached at its ends by a stitching 15 to form a compartment 16 for the receipt of a cable or similar item. Cell 12 is made up of a fabric material 17 which can be attached at its ends by the same stitching 15 that attached the ends of material 14 of cell 11. Thus, a compartment 18 is formed in cell 12 to receive a cable or similar item. Similarly, cell 13 is made up of a fabric material 19 which can be attached at its ends by stitching 15 so that cells 11, 12 and 13 are all attached to each other. A compartment 20 is formed in cell 13 to receive a cable or similar item.
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This application claims priority from U.S. provisional patent application Ser. No. 61/403,806 filed on Sep. 23, 2010, which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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61403806 | Sep 2010 | US |