HK1050567B - Conduit insert for optical fiber cable - Google Patents

Description

Pipeline plug-in unit for optical fiber cable

Technical Field

The present invention relates generally to a round tube of the type that may be used to enclose underground cables such as fiber optic cables, coaxial cables, and the like. The invention relates in particular to a partitioning device which can be inserted into a duct to divide the duct into different zones. The invention is particularly directed to a flexible, elongate separating device which can be inserted into a pipe which has been buried in the ground and in which a cable has been laid, with angled bends or the like.

Cables such as fiber optic communication cables are often laid down underground for long distances, sometimes even several kilometers. It is known to those skilled in the art that cables are buried in the ground so that the cables and cable support means do not gather above ground. Furthermore, the cable is laid underground to protect it from various weather conditions and other potentially harmful conditions.

Background

It is known to those skilled in the art that cables are laid in pipelines to provide more complete protection of underground cables. Such pipes are typically formed from lengths of polyvinyl chloride tubing or the like laid in the ground. Then, blow a rope through the pipeline, tie a communication cable with the one end of rope, draw the rope thereby to drag the cable through the pipeline. Once the cable is in place in the conduit, the conduit protects the cable from various weather conditions, water, and other elements.

It has been found that certain rodents sometimes bite through underground pipes. Thus, most underground pipes used are over two inches in diameter, making them large enough to prevent damage by most rodents. While such ducts provide good protection for communication cables, there is a significant amount of unused space or "dead" areas within such ducts. With the invention of fiber optic cables, a cable may therefore be only a half inch or less in diameter, which results in more dead space in a typical conduit.

When a pipe is buried, a second communication cable may be run at the same location. Therefore, it is preferable to use the dead space of the existing pipeline rather than laying a new section of pipeline from the viewpoint of saving time and money. However, it has been found that it is difficult to insert a second cable alone in a conduit having one cable already. When the rope is blown into a conduit in which one cable is already present, or when a second cable "snakes" through the conduit, they are generally caught by the first conduit and are thus prevented from being inserted into the second cable.

It has been proposed to insert a divider into the duct to divide the duct into sections so that insertion of the second cable is made easier. The problem with this is that when laying long lengths of pipe, where there are always some undulations, sometimes also design bends are encountered, such as at underground passages etc., where the known separators can be difficult, if not impossible, to lay.

There is therefore a need for an apparatus for dividing or separating a conduit, such as an underground communication cable conduit, into different sections. The device must be capable of being inserted into a pipeline that has been buried in the ground, which may be undulating over miles, where sharp bends may also be present. There is also a need for a partitioning apparatus that better utilizes the space within the duct.

Disclosure of Invention

The present invention includes a flexible innerduct structure configured to receive a cable in a conduit. The innerduct comprises a pair of adjacent strips of flexible material joined along longitudinal edges to form a channel through which a cable can be run longitudinally through the innerduct structure between the layers. A major feature of the invention is that adjacent layers have different widths between their longitudinal edges so that the wider layer bulges away from the narrower layer to form an opening for the passage.

The present invention provides a flexible insert for insertion into a fibre optic conduit, comprising: a multiple pass knitted component having a plurality of knitted strips joined together to form a pass between adjacent knitted strips, one of the strips having a predetermined width, second and third strips being applied to said one strip, respectively, said one strip having a width less than the width of said second and third strips; and a means of sealing all the strips intermittently at their edges.

The present invention also provides a multi-channel woven insert for fiber optic cable conduits, comprising: at least four strips of woven material applied one to the other, each of said strips being elongate and having warp yarns extending in a longitudinal direction, said warp yarns being a monofilament of denier from 200 to 1000; and a means for intermittently sealing the longitudinal edges of the strips of fabric to form channels between each adjacent strip.

Other features of the invention relate to the material from which the innerduct structure is constructed. These characteristics include the structure of the material, such as its woven structure, as well as the physical properties of the material, such as melting point, tensile strength, elongation, coefficient of friction, crimp resistance, and compression recovery.

Drawings

The invention will become more apparent with reference to the following description and the accompanying drawings. Wherein:

FIG. 1 is an isometric view of a conduit insert device incorporating a first embodiment of the present invention;

FIG. 2 is a cross-sectional view of the device of FIG. 1;

FIG. 3 is an isometric view of the device of FIG. 1 in a pipeline;

FIG. 4 is a cross-sectional view of an apparatus including a second embodiment of the present invention;

FIG. 5 is a partial view of a fiber optic cable used in the present invention;

FIG. 6 is a schematic illustration of a strip of innerduct layer material constructed in accordance with the invention;

FIG. 7 schematically illustrates the apparatus of FIG. 4 on a test fixture; and

fig. 8 is a schematic illustration of another innerduct layer material constructed in accordance with the invention.

Detailed Description

Referring now to the drawings, reference numeral 10 designates an insert, also referred to herein as an inner tube, which is inserted into a fiber optic cable duct 12. As shown in fig. 3, there is one inner pipe 10 in the pipe 12, and it is obvious that a plurality of inner pipes as the inner pipe 10 may be inserted into one pipe 12 according to the diameter of the pipe 12. For example, three such inner tubes may be inserted into a 4 inch diameter tube to form 9 channels into which fiber optic cables can be inserted.

Each of the inner tubes 10 is interconnected by fabric layers 16, 18, 20, 22, etc. to form a plurality of channels 14. In the first embodiment of the invention, each inner tube 10 has three channels 14 formed by the layers 16, 18, 20, 22 described above. The layers 16, 18, 20, 22 are joined to one another along their opposite longitudinal side edge portions by overlapping the edge portions 25 of the lowermost layer 16 with the edge portions of the other layers and joining the layers together with a sewing thread 24 or other suitable means such as ultrasonic welding. Although the figure shows an inner tube with three channels made up of four fabric layers, it is obvious that the inner tube may be made up of more than three channels made up of more than four fabric layers.

This fabric material is preferably a flexible material so that the inner tube 10 can be pulled through the tube 12 without interference or excessive heat generation. The fabric material may take a variety of other forms so that a cable in one of the channels 14 does not encounter a cable in an adjacent channel 14. To this end, the layers 16, 18, 20, 22 in the first embodiment are all 100% flat-woven nylon material having a 520 denier per filament, woven with a weft and warp density (pick and end count) of 38.5 in both the weft and warp directions, and woven to have a weft and warp density of 40X 40. The fabric weighed 6.0 oz per yard (oz.yd). It is apparent that the denier per filament can vary between 200 and 1000 denier and that the weft and warp densities can also be varied to provide the desired coverage to effectively prevent contact between fiber optic cables.

As noted above, the yarn is preferably a 520 denier nylon 6 monofilament, but another yarn such as 520 denier polyester may be used, so long as it has the desired characteristics.

The inner tube 10 is preferably constructed in the following manner. The fabric layers 16, 18, 20, 22 are woven into a rectangular shape and then slit into strips in the warp direction, with the width of the central strip 20 being the smallest, the adjacent strips 18 and 22 being wider, and the strip 16 being the widest, so that when the strips 16-22 are joined along their longitudinal edge portions, the wider strips 16, 18, 22 bulge out to form the channel 14. The strips 16, 18, 22 are cut and laid between adjacent strips. The longitudinal side edge portion 25 of the lowermost strip 16 is then folded over and folded over the longitudinal side edge portions of the other strips, and then sewn to form the innerduct 10 shown in fig. 1. Such as using a device that intermittently seals all the strips at their edges.

The inner pipe 10 is made long so that it can be inserted into a previously installed pipe 12. Each layer 16-22 is formed by sewing or otherwise joining the strips of fabric material end-to-end in succession to form respective lengths. A pull cord 26, preferably a woven plastic tape or a woven plastic rope, is attached to one end of a fiber optic cable (not shown) and then pulled through the passageway 14 by grasping the other end of the pull cord 26. The pull cord 26 is preferably placed over the layers 16, 18, 20 prior to the layers 16-22 being partially overlapped along the longitudinal edges.

For example, as shown in fig. 3, an inner tube 10 is inserted into a 4 inch inner diameter pipe 12. The strip fabric layer 20 is 3 inches wide, the layers 18 and 22 are 4 inches wide, and the layer 16 is 6 inches wide. The width of the narrowest layer is therefore less than the internal diameter of the pipe 12. This helps to minimize friction between the inner tube 10 and the pipe 12 as the inner tube 10 is pulled through the pipe 12.

The inner tube is easy to manufacture and is constructed so that the fiber optic cable can be pulled through the passage without obstruction or without the continual build up of heat build up due to friction and without contact or alternating loss between adjacent fiber optic cables within other passages of the insert.

Figure 4 illustrates a second embodiment of a flexible innerduct structure 100 according to the invention. As with the innerduct structure 10 of the first embodiment, the innerduct structure 100 of the second embodiment also includes strip-shaped layers of flexible, braided material 102, 104, 106, 108 joined by stitching 118 along longitudinal edge portions 110, 112, 114, 116 thereof, respectively. Each adjacent pair of layers forms a respective cable channel 121, 123 or 125. According to the invention, each pair of layers has a different width between their longitudinal edge portions, so that the wider of the pair of layers bulges away from the narrower layer, thereby forming an opening for the channel 121, 123 or 125.

As with inner tube 10, the opening of passage 121, 123 or 125 in inner tube 100 facilitates the longitudinal insertion and pulling of cables through passage 121, 123 or 125 by respective pull cords 131, 133 and 135. This is because the space between the layers 102 and 108 helps to prevent them from being dragged along with the cable and thus helps to prevent the inner tube 100 from bunching up in the conduit as the cable and pull cord 131 and 135 move longitudinally through the channels 121, 123 or 125.

As described above, the formation of the cross-sectional portion of the innerduct 10 is accomplished by the different strips of fabric material being interconnected along their longitudinal edge portions to form the overlapping layers 16, 18, 20 and 22. As shown in fig. 4, the overlapping layers 102,104, 106 and 108 of the inner tube 100 are formed by only one strip of web material 140 being folded and interconnected at their longitudinal edge portions. The present invention may also employ two, three, four or more strips of material to form the interleaved layers. Each one of a plurality of continuous strips connected end to form an inner tube having a length that may extend, for example, three to four miles.

Fig. 5 is a partial schematic view of a fiber optic cable 150 housed within an inner tube of the present invention. The cable 150 includes a plastic housing 152 containing a bundle of optical fibers 154. Each layer of the inner tube for receiving the cable 150 is preferably formed of a flexible plastic material, which is specified to have a melting temperature relative to the plastic housing 152 that is not less than the melting temperature of the plastic housing material, and more preferably is greater than the melting temperature of the plastic housing material. This helps to ensure that the cable 150 does not melt through the cable 150 due to sliding friction as the cable 150 is pulled longitudinally through the inner tube. In accordance with a feature of the present invention, the inner tube layer is preferably formed of nylon 6 such that its melting temperature is approximately 220 ℃.

The burn-through resistance of the cable may also be specified with reference to the pull cord tube cut test results, which are generally similar to the known Bellcore pull cord tube cut test. According to a feature of the invention, the material of the inner tube layer is preferably specified as: polypropylene rope having a diameter of 0.25 will not melt through the sample of the innerduct structure when pulled through the sample at a speed of 100 feet per minute for at least 90 seconds under 450 pounds of tension.

The material of the inner tube layer may be further specified with respect to the material of the pull cord. According to a feature of the invention, the material of the layer and the material of the traction cable preferably have respective elongations which are substantially equal at a given tensile force. If the elongation of the inner tube is significantly different from the elongation of the traction cable. When these structures are pulled together through a pipe in which they are housed, one structure may lag relative to the other. The elongation of the layer material and the pull cord material at peak tensile load, i.e. just prior to stretch-breaking, is preferably no greater than 75%, and preferably between about 15% and 60%. A more preferred range is about 25% to 40%. For example, nylon 6 is a preferred material having an elongation of about 40% at peak tensile load. Polyester is another preferred material having an elongation at peak tensile load of about 25%.

Other features of the invention relate to the tensile strength of the material of the inner tube layer. In an innerduct of the invention, the tensile strength of each layer in the longitudinal direction is preferably at least about 12.5 pounds per inch of width. The tensile strength of each layer in the machine direction may be in the range of about 12.5 to 300 pounds per inch width, and more preferably in the range of about 50 to 250 pounds per inch width. Most preferably, however, each layer has a tensile strength in the machine direction in the range of about 100 to 200 pounds per inch of width. For example, each of the layers 102, 104, 106 and 108 within the innerduct 100 can be constructed of a woven fabric material having warp and weft yarns comprised of nylon 6 and a longitudinal tensile strength of about 150 pounds per inch width.

The interconnected layers together as a unit form an innerduct structure having a longitudinal tensile strength of at least about 90 pounds per inch of width. But may have a tensile strength in the machine direction in the range of about 50 to 5000 pounds per inch width, more preferably in the range of about 125 to 4500 pounds per inch width, and most preferably in the range of about 1250 to 4000 pounds per inch width.

Other features of the present invention may be described with reference to fig. 6. In particular, FIG. 6 is a schematic representation of a woven innerduct fabric material strip 160 for use in the present invention. The strip has warp yarns 162 extending lengthwise and weft yarns 164 across its width. As shown by way of example in fig. 4, the weft yarns 164 are flexible and have a certain stiffness or a certain resistance to curling, which helps the wider layers in the inner tube to maintain their bowed state relative to the narrower layers without curling or creasing to adjacent narrower layers. Such curling or creasing is not substantially considered in the longitudinal direction of the layers. Thus, the warp yarn 162 in FIG. 6 may have a crimp resistance less than the weft yarn 164. The same is true of the preferred embodiment of the strip 160, wherein the warp yarn 162 is comprised of polyester, which has a first crimp resistance; weft yarn 164 is comprised of nylon 6, which has a greater second crimp resistance. Polyester is preferably used for the warp yarns 162 to minimize the difference in elongation with the pull cord, which is also preferably comprised of polyester.

Curl resistance can be expressed by the curl recovery angle. The crimp recovery angle is the degree to which the sample returns toward a flat open condition after folding the sample material 180 degrees about a fold line according to AATCC method 66. For example, a particular innertube layer constructed in accordance with the invention can have a warp of thermoset polyester and a fill of nylon 6. The material has been found to have a crimp recovery angle of 70 degrees in the warp direction and 135 degrees in the weft direction; a material similar to natural color polyester, but not thermoset polyester, has a crimp recovery angle of 50 degrees in the warp direction and 125 degrees in the weft direction; a material having thermoset polyester yarns in both the warp and fill directions has a crimp recovery angle of 90 degrees in the warp direction and 75 degrees in the fill direction; whereas a similar material having only greige nylon yarns in the warp and fill directions had a crimp recovery angle of 130 degrees in the warp direction and 120 degrees in the fill direction.

The material of the inner pipe layer must be sufficiently rigid so as not to collapse or bunch up under the action of the pull cord and cable, but sufficiently flexible so as to be able to be pulled easily through the corners and undulations of the pipe in which the inner pipe is loaded. The INDA IST90.3 test procedure is one method of determining the stiffness of the innerduct layer material. In this process, a sample of flexible material is first laid on the grooved surface and then a blade is used to force the material through the slot, the result being expressed as the force applied. In accordance with the present invention, a strip of innerduct layer material extending longitudinally through the slot is forced to bend along a transversely extending fold line, preferably in the range of about 950 to 1750 grams for a test of stiffness of the strip. A strip of innerduct layer material extending transversely across the slot is forced to bend about a longitudinally extending fold line, preferably in the range of about 150 to 750 grams as measured by a stiffness test. The strip of innerduct layer material is therefore less rigid in width; the corresponding greater flexibility in its width helps to avoid creasing and thus helps to maintain the wider layer of the inner pipe in a bulged condition relative to the adjacent narrower layer, as described above with reference to figure 4. For example, the weft yarn 164 of the woven innerduct fabric material strip 160 (FIG. 6) is comprised of nylon 6, which has been found to have a stiffness test result of between about 350 and 550 grams; the warp yarn 162 is made of polyester. The yarn has been found to have a stiffness test result of between about 1250 and 1450 grams.

The coefficient of friction of the innerduct layer material of the present invention can also be specified. In accordance with a feature of the present invention, the inner ply material preferably has a dry static coefficient of friction of between about 0.010 and 0.500 based on the high density polyethylene material having a force along the longitudinal axis of the material. More preferably, the range is from about 0.025 to about 0.250, and most preferably from about 0.035 to about 0.100. For example, a woven innertube layer having polyester warp yarns and nylon 6 fill yarns has been found to have a dry static coefficient of friction of 0.064 when the material is high density polyethylene with the longitudinal axis in the direction of force. And a similar material with warp yarns of thermoset polyethylene has a corresponding coefficient of friction of about 0.073; a material having a corresponding coefficient of friction of about 0.090, being a thermoset polyester yarn in both the warp and fill directions; a material having greige nylon 6 base yarn in both the warp and fill directions has a corresponding coefficient of friction of about 0.067. The coefficients of friction of the four materials are 0.085, 0.088, 0.110, and 0.110, respectively, when force is applied along the transverse axis. These materials, still high density polyethylene, have a coefficient of dynamic or sliding friction along the longitudinal axis of 0.063, 0.56, 0.058, and 0.049 respectively. Accordingly, the dynamic coefficients of friction along the transverse axis of force are 0.064, 0.067, 0.078 and 0.075, respectively. While these tested sliding friction coefficients are most preferred, the invention also encompasses a broader range, for example, from about 0.0050 to 0.1250, also encompasses intermediate values in this range from about 0.0075 to about 0.0625, and a narrower range from about 0.0100 to about 0.0250.

Other features of the invention relate to the open structure of the channel in the inner tubular structure. In addition to adjacent layers having different widths, the present invention preferably further includes a characteristic of the material of each layer that is related to the open structure of the channel between and formed by the layers. This material property of the layers is a spring-like force that maintains the innerduct structure in a free standing condition, as shown for example in FIG. 7 for the innerduct structure 100. When the surface 200 is fully flattened against the surface 200 by the actuator 202 under the applied test force F, and when the actuator 202 is retracted and the force F is released, the inner tubing 100 preferably springs back fully or substantially fully to its original free standing condition. By "fully flattened out" is meant that the wider layers 104, 106 and 108 deflect and deflect onto the narrowest layer 102 and until the applied test force F reaches a peak where there is no further compression and the inner tube 100 is not damaged. This fully flattened condition includes tucking between overlapping pleats of the wider layers 104, 106 and 108. The inner tube 100, or another inner tube constructed in accordance with the present invention, is preferably not recompressed in the same manner when the peak test force applied is about 85% to 100% of the previous peak test force. This means that the inner tube can retain its open structure to a greater extent and the cable passes through the cable passage through this opening.

Fig. 8 is similar to fig. 6 and shows another strip 200 of innertube layer material constructed in accordance with the invention. Like the strip 160 shown in fig. 6, the strip 200 includes a woven structure having warp yarns 202 and weft yarns 204. The strip 200 further includes a spacer 206 which prevents air from flowing through the strip 200 between the warp 202 and weft 204, the sealed strip allowing the cable to be blown through the innerduct structure without pneumatic pressure loss from the passage of air outwardly through the layer.

The sealing strip may be used to form all layers of the innerduct, but is more preferably used to form the outermost layer of the innerduct structure. For example, the outermost layers 16 and 22 of the innerduct structure 10 described above may be formed from a pair of like strips 200; one strip, like strip 200, may be used to form all of the layers 102 and 108 of the innerduct structure 10 described above. In the embodiment shown in FIG. 8, separator 206 is a thin layer of plastic material that is bonded to warp yarns 202 and weft yarns 204 during a hot pressing process. If the inner tubular structure comprises a plastic air-insulating body like the layer 206 at a position facing the inner side of the cable channel, the air-insulating body is preferably formed of a plastic material having a melting temperature not lower than the melting temperature of the plastic sheath material of the cable blown through the channel.

While the present invention has been described with reference to preferred embodiments, those skilled in the art will also recognize many modifications, variations, and adaptations of the present invention. This improvement is made. Variations and modifications are within the scope of the claims.

Claims (70)

1. A flexible insert for insertion into a fiber optic conduit, comprising:

a multiple pass knitted component having a plurality of knitted strips joined together to form a pass between adjacent knitted strips, one of the strips having a predetermined width, second and third strips being applied to said one strip, respectively, said one strip having a width less than the width of said second and third strips; and a means of sealing all the strips intermittently at their edges.

2. The insert of claim 1 wherein each of said woven strips has a monofilament warp yarn.

3. The insert of claim 2, wherein the warp yarns extend in a longitudinal direction of the insert.

4. The insert of claim 3, wherein each of said woven strips has a monofilament weft yarn.

5. The insert of claim 4, wherein said monofilament yarns have a denier of between 200 and 1000.

6. The insert of claim 5, further comprising a fiber optic pull cord between each of said adjacent braid strips.

7. The insert of claim 6, wherein the second or third strip is wider than the other strips and is sewn after folding the side edges of the other strips to form a composite structure.

8. The insert of claim 7, wherein all of the strips are flat woven.

9. A multi-channel woven insert for fiber optic cable ducts, comprising: at least four strips of woven material applied one to the other, each of said strips being elongate and having warp yarns extending in a longitudinal direction, said warp yarns being a monofilament of denier from 200 to 1000; and a means for intermittently sealing the longitudinal edges of the strips of fabric to form channels between each adjacent strip.

10. The insert of claim 9, wherein each of said fabrics has a monofilament weft yarn.

11. The insert of claim 9, wherein a first one of the at least four strips has a predetermined width, second and third ones of the at least four strips on opposite sides of the first strip are wider than the one strip, and a fourth one of the at least four strips is contiguous with the second or third strip and is wider than the one, second or third strip.

12. The insert of claim 11, wherein the edges of said fourth strip overlap and are sewn to the edges of said one, second and third strips.

13. The insert of claim 12, wherein a pull strip is positioned between each of said adjacent braids.

14. A conduit insert for an electrical cable, comprising:

a flexible innerduct structure configured to contain a cable within a conduit, said innerduct structure comprising at least a pair of adjacent, strip-shaped, flexible material layers joined along their longitudinal edge portions to form a channel through which the cable can extend longitudinally between said layers;

the layers have different widths between the longitudinal edges so that the wider layer bulges away from the narrower layer to form an open structure of the channel.

15. The insert of claim 14, wherein the pair of layers is one of a plurality of pairs of adjacent and interconnected strip-shaped layers of flexible material, and each pair of layers is connected along portions of their longitudinal edges to form and enclose the channel of a respective one of the cables, with each pair of layers having a different width between their longitudinal edges.

16. The insert of claim 15, wherein the plurality of pairs of layers are formed by folded portions of the sheet of flexible elongated material.

17. The insert of claim 15, wherein the pairs of layers are interconnected along the longitudinal edges.

18. The insert of claim 17, wherein said pairs of layers are attached to one another in overlapping relation.

19. The insert of claim 18, wherein the pairs of layers are attached to each other by stitching.

20. The insert of claim 14, further comprising the conduit containing the inner tubular structure therein.

21. The insert of claim 20, wherein the width of the narrower layer is less than the inner diameter of the conduit.

22. The insert of claim 20, further comprising a cable passing longitudinally through said passage, said cable having a sheath of plastic material having a first melting temperature, said layers each being of plastic material having a second melting temperature not lower than said first melting temperature.

23. The insert of claim 14, further comprising an elongated pull cable extending longitudinally through the passageway.

24. The insert of claim 23, wherein the inner tubular structure and the pull cable have respective elongations that are substantially equal at a given tensile load.

25. The insert of claim 24 wherein the elongation at peak tensile load is no greater than 75%.

26. The insert of claim 25, wherein the elongation is in the range of 15% to 60%.

27. The insert of claim 26, wherein the elongation is 50%.

28. The insert of claim 26, wherein the elongation is in the range of 25% to 40%.

29. The insert of claim 28, wherein the elongation is 25%.

30. The insert of claim 14 wherein the flexible material is a fabric material.

31. The insert of claim 30 wherein said fabric material is a woven fabric material.

32. A conduit insert for an electrical cable, comprising:

a flexible structure comprising flexible material abutting in such a way as to form at least two longitudinal channels, each channel being capable of enclosing and carrying a cable;

wherein the structure forms an open channel resiliently biased toward and readily foldable in the transverse direction, an

The flexible material has an elongation of less than or equal to 40% at peak tensile load.

33. The insert of claim 32, wherein the elongation is in the range of 25% to 40%.

34. The insert of claim 33, wherein the elongation is 25%.

35. The insert of claim 32 wherein the structure is configured to contain a cable, the cable having a sheath of plastic material, and the flexible material is a flexible plastic material defined by, relative to the material of the plastic sheath: so that the melting temperature is not lower than the melting temperature of the plastic sheath material.

36. The insert of claim 35, wherein the flexible material has a melting temperature of at least 220 ℃.

37. The insert of claim 32, wherein the structure is formed from a plurality of strip-shaped layers joined along their longitudinal edge portions to form the channel.

38. The insert of claim 37, wherein each layer has a longitudinal tensile strength of at least 12.5 pounds per inch width.

39. The insert of claim 38, wherein the longitudinal tensile strength of each layer is in the range of 12.5 to 300 pounds per inch of width.

40. The insert of claim 39 wherein the longitudinal tensile strength is in the range of 50 to 250 pounds per inch of width.

41. The insert of claim 40 wherein the longitudinal tensile strength is in the range of 100 to 200 pounds per inch of width.

42. The insert of claim 41 wherein the longitudinal tensile strength is 150 pounds per inch width.

43. The insert of claim 37, wherein the lamination provides the flexible structure with a longitudinal tensile strength of at least 90 pounds per inch width.

44. The insert of claim 37 wherein the lamination provides the flexible structure with a longitudinal tensile strength in the range of 50 to 5000 pounds.

45. The insert of claim 44 wherein the longitudinal tensile strength is in the range of 125 to 4500 pounds.

46. The insert of claim 45 wherein the machine direction tensile strength is in the range of 1250 to 4000 pounds.

47. The insert of claim 32 wherein the flexible material has a lateral crimp recovery angle of between 50 degrees and 130 degrees.

48. The insert of claim 47 wherein the flexible material is a woven fabric material.

49. The insert of claim 32, wherein the flexible material has a dynamic coefficient of friction of less than 0.1250 when the direction of force is the longitudinal axis based on high density polyethylene on the material.

50. The insert of claim 32 wherein the flexible material has a dry static coefficient of friction in the range of 0.010 to 0.500 based on high density polyethylene on the material with the direction of force being the longitudinal axis.

51. The insert of claim 50 wherein the range is from 0.025 to 0.250.

52. The insert of claim 50 wherein the range is from 0.035 to 0.100.

53. The insert of claim 50 wherein the flexible material is a woven fabric and the range is from 0.064 to 0.090.

54. The insert of claim 32, wherein the flexible material has a dry sliding coefficient of friction in the range of 0.0050 to 0.1250 when the direction of force is the longitudinal axis based on high density polyethylene on the material.

55. The insert of claim 54 wherein the range is from 0.0075 to 0.0625.

56. The insert of claim 54 wherein the range is from 0.010 to 0.025.

57. The insert of claim 54 wherein the flexible material is a woven fabric and the range is from 0.049 to 0.063.

58. The insert of claim 32 wherein said flexible material is selected such that a 0.25 inch diameter polypropylene rope will not melt through said structural specimen when pulled through said specimen under 450 pounds of tension for at least 90 seconds at a rate of 100 feet per minute.

59. The insert of claim 58 wherein the flexible material is a thermoset woven plastic material.

60. The insert of claim 32 wherein said structure has a degree of compression recovery such that said structure compresses from said free standing condition to said applanation condition under a first peak test load and does not recompress to said applanation condition under a second peak test load, said second peak test load being less than 85% of said first peak test load.

61. The insert of claim 60 wherein the flattened condition is a fully flattened condition and the flexible material is in the form of a sheet with folds formed between overlapping pleats of the wider sheet.

62. The insert of claim 32, wherein the flexible material is a flexible woven fabric having warp yarns that combine to provide the woven fabric with a first crimp recovery angle and weft yarns that combine to provide the woven fabric with a second, greater crimp recovery angle.

63. The insert of claim 62, wherein the first crimp recovery angle is 70 degrees and the second crimp recovery angle is 120 degrees.

64. The insert of claim 62, wherein the warp yarns are comprised of polyester and the weft yarns are comprised of nylon.

65. The insert of claim 32, wherein the flexible material has a first bending stiffness that is bending about a longitudinally extending fold line and a second greater bending stiffness that is bending about a laterally extending fold line.

66. An insert according to claim 65 wherein the first stiffness is in the range 150 to 750 grams and the second stiffness is in the range 950 to 1750 grams.

67. The insert of claim 65 wherein the first stiffness is in the range of 350 to 550 grams and the second stiffness is in the range of 1250 to 1450 grams.

68. The insert of claim 65 wherein said flexible material is comprised of a flexible woven fabric having weft yarns and warp yarns, the weft yarns collectively providing said woven fabric with said first stiffness and the warp yarns collectively providing said woven fabric with said second, greater stiffness.

69. The insert of claim 32, wherein the structure comprises a plurality of strips configured to be connected along their longitudinal edge portions to form the channel, wherein at least one of the strips is sealed such that air flow does not pass through the strip.

70. The insert of claim 32, wherein the flexible structure is formed from a sheet of the flexible material.