Abstract
A new use for Litz wire is described. Litz wire is used as bare tracer wire, as tracer wire within known woven polyester or aramid fiber pull tape and as tracer wire within a known marker tape. Litz marker tape is described which is a novel type of marker tape is wherein Litz wire is incorporated into the structure of conventional marker tape so that the marker tape may be remotely located and mapped once it has been buried underground. In addition a method is disclosed for determining the proper size of an individual strand of wire in a Litz wire bundle which is going to be used as Litz pull tape or as Litz marker tape. In addition a method of emplacing Litz wire tracer wire or marker tape using a horizontal boring machine is disclosed.
Claims
1. A method for a new use for Litz wire comprising using Litz wire as tracer wire to mark the location of an underground utility.
2. A method for a new use for Litz wire comprising using marker tape with Litz wire incorporated therein to mark the location of an underground utility.
3. A method for a new use for Litz wire comprising using Litz wire incorporated in a conventional fabric pull tape to mark the location of an underground utility.
4. A Litz pull tape comprising a woven polyester tape with a Litz wire tracer wire embedded within said woven polyester tape.
5. A Litz pull tape comprising a woven aramid fiber tape with a Litz wire tracer wire embedded within said woven aramid fiber tape.
6. A marker tape assembly comprising: a first layer with a first predetermined width and with an indefinite length comprising a colored polyethylene or other moisture or soil resistant synthetic plastic tape with said first layer having an upper and a lower surface; a substantially straight, open channel with a predetermined cross-section formed on said upper surface of said first layer with said channel running along the length of said first layer; a Litz wire tracer wire of indefinite length and having a cross-section less than said predetermined cross-section positioned within and running along said channel; a second layer with a second predetermined width and with an indefinite length comprising a colored polyethylene or other moisture or soil resistant synthetic plastic tape with said second layer also having an upper and a lower surface; the lower surface of said second layer being laminated to the upper surface of said first layer in order to close said open channel and seal said Litz wire within said marker tape assembly.
7. The marker tape assembly of claim 6 wherein said first predetermined width and said second predetermined width are substantially identical.
8. The marker tape assembly of claim 6 wherein colored warning indicia are imprinted on at least one of the surfaces of said first or second layer.
9. The marker tape assembly of claim 8 wherein said colored warning indicia comprise alternating and contrasting colored stripes running across the predetermined width of at least one of said first or second layers.
10. The marker tape assembly of claim 9 wherein written warning indicia are imprinted on one of said upper or said lower surface of at least one of said layers.
11. A new use for Litz Wire as marker wire comprising burying the Litz Wire near an underground utility so its location can be detected with conventional marker wire locating devices thus enabling determination of the location of the buried utility.
12. A method for a new use for wire woven into and embedded within a woven fabric tape along the longitudinal extent of the woven fabric tape comprising: drilling an underground borehole with the drill head of a directional drilling machine, attaching the wire woven into and embedded within a fabric tape to the drill head, attaching a utility line to the drill head, withdrawing the drill head with the utility line and the wire woven into and embedded within a fabric tape attached thereto back along the borehole in a pullback operation, and thus emplacing underground the wire woven into and embedded within a fabric tape at the same time as the utility line is emplaced underground.
13. The method of claim 12 wherein said wire is copper marker wire.
14. The method of claim 12 wherein the woven fabric tape comprises polyester fibers.
15. The method of claim 12 wherein the woven fabric tape comprises aramid fibers.
16. A combination of Litz wire and woven fabric tape for use as marker tape wherein the Litz wire is embedded along the longitudinal extent of the woven fabric tape and woven therein except for a predetermined portion at one end of the woven fabric tape which portion is free of the Litz wire so that said portion may be secured to a drill stem and successfully emplaced as marker wire along with a utility line during a pullback operation.
17. The method of emplacing marker wire and a utility line at the same time in a pullback operation comprising the steps of: drilling an underground, borehole using a known directional drilling machine comprising a known drilling head, from a fixed starting position on the soil surface to a target site near or on the soil surface but separated from the known starting position by a predetermined distance, affixing a utility line to the drilling head at the target site in a known manner, providing a marker tape comprising a woven fabric tape with Litz wire embedded therein along the longitudinal extent of said tape except for a predetermined portion at one end of the woven fabric tape, affixing said marker tape to the drilling head at the target site by tying said predetermined portion of said marker tape to said drilling head, and withdrawing said drilling head back through the borehole to the fixed starting position using a pullback step, whereby the utility line is installed in the borehole and the marker tape is also installed in the borehole at the same time during the pullback step.
18. The method of claim 17 wherein the step of providing a marker tape comprising a woven fabric tape with Litz wire embedded therein along the longitudinal extent of the tape further comprises using a woven fabric tape comprising polyester fibers.
19. The method of claim 17 wherein the step of providing a marker tape comprising a woven fabric tape with Litz wire embedded therein along the longitudinal extent of the tape further comprises using a woven fabric tape comprising aramid fibers.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 shows a first embodiment of a prior art marker tape without tracer wire.
[0031] FIG. 2 shows a second embodiment of a prior art marker tape without tracer wire.
[0032] FIG. 3 shows a third embodiment of a prior art marker tape which has tracer wire.
[0033] FIG. 4 shows a cross section of the marker tape with tracer wire of FIG. 3 along plane A-A of FIG. 3.
[0034] FIG. 5 shows a plan view of prior art tracer wire.
[0035] FIG. 6 shows a cross-section of the tracer wire of FIG. 5 along arrow B of FIG. 5.
[0036] FIG. 7 shows a first cross-sectional view of a conventional wire illustrating the skin effect.
[0037] FIG. 8 shows a second cross-sectional view of a wire further illustrating the skin effect.
[0038] FIG. 9 shows a third cross-sectional view of a wire further illustrating the skin effect.
[0039] FIGS. 10-15 illustrate various known types of Litz wire.
[0040] FIG. 16 shows a conventional horizontal boring operation.
[0041] FIG. 17 shows a conventional boring head for a horizontal boring machine.
[0042] FIG. 18 illustrates a polyester pull tape having tracer wire woven there through.
[0043] FIG. 19 shows a graph illustrating the method for picking the optimum wire size in a Litz wire bundle for use with the invention.
[0044] FIG. 20 shows a view of an underground utility with conventional tracer wire installed for locating purposes.
[0045] FIG. 21 shows a view of the installation of FIG. 20 along the arrow C of FIG. 20.
[0046] FIG. 22 shows a view of an underground utility with a pull-tape incorporating Litz wire installed as tracer wire.
[0047] FIG. 23 shows a view of the installation of FIG. 22 along the arrow D of FIG. 22.
[0048] FIG. 24 shows a plan view of a marker tape according to the invention incorporating Litz wire tracer wire.
[0049] FIG. 25 shows a cross-sectional view of the marker tape of FIG. 24 along section E-E of FIG. 24.
[0050] FIG. 26 shows an example of Litz Wire incorporated within a woven fabric carrier.
[0051] FIG. 27 shows a utility attached to the pulling head of the boring head shown in FIG. 17 and a Litz wire tracer wire attached to the swivel of the boring head shown in FIG. 17.
[0052] FIG. 28 shows a another embodiment of the inventive marker tape using various indicia imprinted thereon.
DETAILED DESCRIPTION
[0053] FIGS. 1-18 have been described supra in the BACKGROUND section or the SUMMARY OF THE INVENTION section of this specificationso they will not be further described.
[0054] FIG. 19 shows the method of determining optimum wire size in a Litz wire bundle for use with Litz Pull Tape or Litz Marker Tape. The operating frequency of the system which will detect the Litz Pull Tape or Litz Marker Tape is presumed known. The total length of the Litz wire and the number of wires [or strands] in the Litz wire is also presumed known. Thus for a given operating frequency, with a given length of Litz wire and a given number of wires or strands in the bundle, the optimum wire [strand]size is that size which will produce the least value of impedance in the Litz wire. This would mean that any current induced in the Litz wire by a detecting system would be able to produce the strongest magnetic fields for detection. FIG. 19 plots |Z|, X.sub.L and R.sub.DC for a given length of Litz wire with a given number of wires [strands] in the Litz wire bundle and for a given operating frequency. |Z| is a function of the sum of capacitive reactance [X.sub.L] and DC resistance [R.sub.DC]. The x axis in FIG. 17 is the wire size of an individual wire in the Litz wire bundle and the size decreases to the right. The y axis is |Z|, X.sub.L and R.sub.DC increasing upwardly. The absolute value of impedance |Z| is determined by the following equation.
|Z|=X.sub.L+R.sub.DC[1]
In equation [1] X.sub.L is equal to the Inductive reactance which is governed by equation [2].
X.sub.L=L=2fL[2]
In equation [2] is the frequency or 2f and L is the inductance of the wire in henries.
[00001]
[3]
[0055] In equation [3] is the DC resistance constant for the type of wire used in the bundle, L is the length of the wire and the remaining variables are self-explanatory. It can be seen that the plot of X.sub.L decreases with decreasing wire size and the plot of R.sub.DC increases with decreasing wire size. Where the two curves meet, you get the minimum value of |Z| and this is the optimum wire size. This is also shown by the plot of |Z| which is the sum of X.sub.L and R.sub.DC. Where the plot of |Z| shows the minimum value is where the X.sub.L and R.sub.DC curves cross. Applicants have found that by using Litz wire as tracer wire instead of solid copper or copper coated steel wire that there is a significant increase in the effective surface area of the Litz wire tracer wire. For example the use of Litz wire as tracer wire can increase the surface area of the wire by about a factor of 4. For example a Litz wire tracer wire that has an equivalent cross-section to a 16 gauge solid copper wire can have about 4 times the wire surface area that the solid wire has. Since induced current is a function of the wire surface area, this will dramatically increase the current induced in the Litz wire tracer wire by known locating and mapping devices. The increase in induced current will result in much greater induced magnetic signal strength when the Litz wire tracer wire is interrogated by conventional locating and mapping transmitters such as those discussed supra in [0010] and [0011]. This, in turn, will make the Litz wire tracer wire much easier to locate.
[0056] FIG. 20 shows a view of a non-metallic underground utility 45 [in this example, pipe] being buried approximately 2 feet below ground surface 40. Since underground utility 45 is non-metallic, it is thus not detectable from surface 40 by known locating and mapping techniques. To remedy this, a tracer wire 41 is buried approximately 6 inches directly above non-metallic underground utility. This tracer wire is conventional Litz wire chosen from any of the types shown in FIGS. 10-15 or any other known type of Litz wire. The invention is the use of Litz wire as tracer wire in this type of application. FIG. 21 is a view of the installation of FIG. 20 taken along arrow C of FIG. 20.
[0057] FIG. 22 illustrates a non-metallic underground utility 48 buried approximately 2 feet below the surface 20. To provide a means to locate and map non-metallic underground utility 48 at a later time Litz pull tape 47 is buried approximately 6 inches directly above non-metallic underground utility 48. Litz pull tape 47 comprises, according to the invention, a known polyester pull tape incorporating any type of Litz wire such as those shown in FIGS. 10-15 or any other type of Litz wire. FIG. 23 is a view of the installation of FIG. 22 taken along arrow D of FIG. 22. The advantage of using Litz pull tape is that the non-metallic underground utility may be located and mapped using conventional surface techniquessuch as those described above in [0011] and [0012]. However, the use of Litz pull tape also gives advance warning of the presence of the underground utility in a manner similar to marker tape because the polyester pull tape is strong enough to be pulled to the surface by excavation equipmentthus warning the excavation crew of the presence of the underground utility. To make it even more clear to the excavation crew that they are about to dig into an underground utility with possibly disastrous results, the Litz pull tape can be colored or have warning indicia emplaced on the exterior surface thereof in much the same fashion as is disclosed below for applicants marker tape.
[0058] FIG. 24 illustrates a marker tape 100, according to the invention, incorporating Litz wire 80 therein as tracer wire. Applicants call the inventive marker tape Litz marker tape. The marker tape is similar in construction to that of Allen '533 as shown therein in FIGS. 3 and 4. This marker tape is also illustrated in FIGS. 3 and 4 of the instant disclosure and described supra in [0008]. The inventive marker tape incorporating Litz wire as tracer wire is shown in FIGS. 24 and 25 of applicants' drawings. In the Allen '533 disclosure, tracer wire 8 was embedded within his marker tape in a zigzag fashion. This is not possible when using Litz wire as tracer wire as the Litz wire must be installed in a generally straight line on the marker tape to avoid interference during the detection process. If the Litz wire were installed in a zigzag or sinusoidal manner within marker tape 100, some of the current induced in the tracer wire during detection by conventional location and mapping devices will cancel out the induced current in other sections of the wirethus it must be straight to function well.
[0059] With the foregoing in mind, marker tape 100 as shown in FIGS. 24 and 25 comprises a lower layer 70 of a colored polyethylene or other moisture and soil-resistant synthetic plastic tape having a relatively straight channel 75 formed therein. Litz wire 80 is emplaced within channel 75 to act as tracer wire for marker tape 100. Again, Litz wire 80 could be of any construction for Litz wire. A number of such constructions are shown in FIGS. 10-15, but any type of Litz wire construction could be used. The invention is providing Litz wire within the marker tape as tracer wire. FIG. 25 is a cross-sectional view of marker tape 100 taken along section E-E of FIG. 24. Laminated to the upper surface of lower layer 70 is another layer 90 also made of colored polyethylene or synthetic plastic. Tape 100 may be color coded to the type of underground utility and may have soil contrasting reflective stripes [shown in FIG. 28] to aid in tape detention. Tape 100 will be color coded in the accepted coding for the type of utility line being protected. The uniform color code generally accepted in the industry to identify underground facilities is as follows: Redelectric power lines; Yellowgas, oil or steam lines; Orangetelephone, police and fire communications and cable television; Bluewater lines; and Greensewer lines.
[0060] It is also possible to incorporate Litz wire of the types shown in FIGS. 10-15 within a woven tape similar to the type of tape used in the electrical industry to pull electrical wires through conduits. This type of pull tape is shown in FIG. 26. FIG. 26 shows pull tape 250 comprising a woven fabric tape 243 which may comprise polyester fibers with Litz Wire 244 woven and incorporated therein. A standard polyester pull tape might be W/P 1250 Lb Polyester Pull Tape [available in large quantities from The Ribbon Factory at 600 North Brown Street, Titusville, Pa., 16354]. This pull tape is approximately inch [1.27 cm] wide, approximately 1/16 inch [approximately 0.16 cm] thick and has a tensile strength of 1250 pounds.sub.f [or approximately 5560 N]. Pull tape is available from other sources with different dimensions and widths and in different strengths, for example, up to 2500 pounds.sub.f [approximately 11,000 N] tensile strength. Pull tape made from aramid fibers is also available. It is possible to obtain an aramid fiber pull tape with a 3000 pounds.sub.f tensile strength [or approximately 13,3430 N]. This tape is approximately inch [approximately 1.59 cm] wide and approximately 1/16 inch [approximately 0.16 cm] thick. It is also possible to obtain polyester pull tape with copper tracer wire incorporated therein. This is illustrated supra in FIG. 18. Applicants have found that it is possible to incorporate Litz wire within standard polyester or aramid fiber pull tape and use the Litz wire as conventional tracer wire within the known pull tapes. Pull tape with Litz wire incorporated therein is called Litz pull tape by applicants. For example, a Litz pull tape could be buried a few inches above, below, or to one side of a non-metallic underground utility when said utility is laid using a conventional trenching operation. A Litz pull tape could also be laid in a horizontal boring operation by tying the Litz pull tape to the boring head [as shown infra in FIG. 27] and being pulled back along with the underground utility. This type of installation has the expected advantage of being locatable from the surface using conventional locating and mapping techniques as discussed supra in [0011] and [0012] and it also has the advantage of having the woven tape act in a manner similar to the Signal Tape disclosed in PCT/US2017/050405. That is, when a Litz pull tape constructed of strong polyester or aramid tape is struck by an excavator bucket it will be pulled to the surface in the same manner as the Signal Tape disclosed in PCT/US2017/050405, thus providing a warning to the excavation crew of a buried underground utility which they may damage if excavation is not halted immediately. One way to increase the effectiveness of this warning is to color the pull tape with brightly colored indicia and to provide written indicia thereon which instructs the excavation crew to cease excavation immediately.
[0061] FIG. 27 shows the inventive Litz Pull Tape 250 shown in FIG. 26 being tied securely to a horizontal boring machine drill head 28 similar to drill head 28 shown in FIG. 17. Drill head 28 is shown ready for a pullback operation with a utility 38 attached to tow head 34. In order to prevent damage to the Litz wire embedded within the Litz pull tape 250, the Litz wire is removed from the last few feet of Litz pull tape 250 and this portion of the Litz pull tape, without any Litz wire therein. is tied to tow head 34, as shown, for pullback so that the pullback forces are transmitted directly to the high strength tape and not to the relatively low strength Litz wire. This part of the operation is called pullback. In this manner, utility lines which may be pipes, power lines or telecommunication cables, etc. may be laid without expensive and time-consuming trenching and backfilling.
[0062] Marker tape 100 is illustrated in FIG. 28. It is similar to marker tape 100 but it has various colored indicia thereon to improve visibility. Marker tape 100 may have cautionary coded indicia 200 in the form of colored stripes extending across tape. If in the illustrated example of FIGS. 20-23, underground utility 45, 48 is assumed to be a water line, then according to the uniform industry code, cautionary stripes 200 would be blue stripes. Marker tape 100 further includes cautionary contrast stripes 220 extending across the tape and forming a contrast in color with color coded stripes 200 as well as with the color of the surrounding soil. Contrast stripes 220 provide a high visibility and high light reflective characteristic to marker tape 100 so that the tape can readily be seen when placed in earth soils whose color is close to the color of color coded stripes 200. In addition, written indicia 105 is imprinted on marker tape 100 either on the outside or as a reverse printing on an inner face of either layer [for example layers 70 or 90 for marker tape 100], as desired. While indicia 200 and 220 make marker tape 100 easier to see in or out of the soil and provide some information on the type of buried utility present, written indicia 105 provides positive identification of the type of buried utility present and may provide other information, as desired.
[0063] The above described embodiments are merely illustrative of the principles of the invention. Those skilled in the art may make various modifications and changes, which will embody the principles of the invention and fall within the spirit and scope thereof.
