Bore spacers for underground installations

Apparatuses and methods are disclosed for assembling ducts or conduits with multi-part spacers for underground installation. Sequential loading of conduits to multi-part spacers, as opposed to older methods of end loading, allows construction workers to easily assemble conduits to a plurality of multi-part duct spacers above-ground. The multi-part loading technique allows sequential loading of conduits into portions of spacers, the spacers having bores to accommodate the conduits. The parts or components of the multi-part spacers may themselves cooperate to mount conduits into a conduit bank or bundle. Thus, conduits are assembled or mounted to a first portion of the spacer, followed by mounting a second portion of the spacer and then additional conduits, which may be mounted to either or both of the first and second portions. Once assembled, the banks or bundles may then be secured with banding and wheeled into a protective casing.

BACKGROUND

Cables for electric power and for communication lines are run underground in order to protect them from above-ground elements and from the interference and damage they would suffer when installed above the ground or on poles or structures. The underground environment may be less hostile in some ways, but the history of underground cables suggests that the underground environment is not to be considered benign.

This patent concerns spacers used for the installation and spacing of communications and power cables under the ground and above ground. Cables for electric power and communication lines are run underground in order to protect them from above-ground elements and from the interference and damage they would suffer when installed above the ground or on poles or structures.

Power and communication distribution cables are typically routed aboveground. They are routed underground when for various reasons, aboveground routes are not permitted or are not possible. Most underground power and communication cables for private homes are dug directly. Power and communications cables for mission-critical installations receive more circumspect treatment. These installations include hospitals, airports, military bases, and major electric transmission lines. For most of these installations, an open cut trench is dug, conduit is placed in the lower portion of the trench in an organized and controlled separation bank, and the conduit is then encased in concrete forming what is commonly known as a concrete encased duct bank. The conduit is most often a round pipe made from plastic but on occasion may be of other shapes and material. Typically, the top of the duct bank is two feet or more below grade. The area between the top of the duct bank and grade is backfilled with sand, gravel, soil, or other appropriate fill. Power or communication cables or both are then pulled into the conduits.

In some instances, however, it is not possible to route an open-cut trench directly to the desired location without disruption. It may therefore be necessary to cross under a highway, a railroad, a waterway, or other obstruction. For these installations, a tunnel must be dug underneath, typically by digging a straight bore or by using directional drilling. A straight bore is typically used for relatively straight installations of less than 500 feet (150 m). After the bore is dug, a casing, typically made of steel, is pulled through the bore and conduit with spacers is pulled into the casing. Directional drilling is typically used for longer bores. In these installations, steel or other casing is most often used, but some installations are casing-less. The directionally drilled casing-less installation method is typically selected when the extra protection offered by a casing and grout is not deemed necessary and economy of the installation is of prime importance.

Underground conduits typically are placed in casings made of steel, high-density polyethylene (HDPE), concrete, fiberglass-reinforced thermoset polymers, such as reinforced thermosetting resin conduit (RTRC), or centrifugally-cast fiberglass reinforced polymers, e.g., Hobas pipe. Other casing materials may also be used. Casing lengths may range from 10 feet to 3,000 feet (3 to 920 m) or longer, with diameter from 4 inches to 60 inches (10 to 150 cm), or larger. The conduits themselves are typically made from high density polyethylene (HDPE), rigid polyvinyl chloride (PVC), fiberglass reinforced epoxy. Other conduit materials may be used. Conduit-in-casing installations are used to route communications and power cables under highways, streams and rivers, railroad track, and other obstructions that, for one reason or another, may not be disturbed. Underground power and communications cables are typically placed in directionally-drilled tunnels or straight-bored tunnels.

Directionally drilled holes normally used for conduit-in-casing installations or casing-less installations refer to a tunnel that starts at grade or in a pit that is slightly below grade. The tunnel goes downward at approximately a 20° angle until it is low enough to go under the obstruction. The obstruction may be 100 feet (30 m) or more below grade. When the tunnel is low enough to go under the obstruction it turns gently and then follows a line parallel to grade. When the tunnel has cleared the obstruction, it sweeps upward at an angle, typically about 40°, and exits at grade. In order to prepare a directionally drilled hole, construction crews start first with a pilot hole. After the pilot hole is installed, reamers of successively larger size are pulled through the hole until the hole is approximately 50% larger than required for the duct bank or casing. As the reamers are pulled through, the hole is kept full of mud made with bentonite to keep the tunnel from caving in or filling with water. Bentonite is a natural clay found in the earth's strata. After the directionally bored hole is completed, the duct bank is pulled into place displacing part of the bentonite.

Straight bores may be prepared in many ways, but are most often accomplished as follows. A boring pit is dug on one side of the obstruction, and a receiving pit on the other side. A length of auger is placed inside steel casing having a similar length and slightly large outer diameter. The auger and casing are placed into the boring pit. Using a special purpose boring machine, which is usually track-mounted, the casing is hydraulically jacked in the direction of the receiving pit while rotating the auger to remove the earth from inside the casing. Successive lengths of casing are welded to each other and successive lengths of auger are attached to remove earth from the casing. When the casing and auger reach the receiving pit, the augers are removed.

Meanwhile, an assembly of the conduits is prepared, the assembly including the conduits and spacers to maintain separation of the conduit in the casing. The spacers are placed along every several feet of conduit length. The assembly of conduits and spacers is then pulled into the casing and grout is placed between the casing and the conduit, filling the space in between them. Grout is a fluid mixture of sand, cement and water. Special additives are sometimes used to make the grout very fluid, to enhance thermal conductivity, or to slow hydration or curing of the grout. After the grout has hydrated, power and communications cables are pulled through the conduits.

One technique used to fill the space is known as the sacrificial grout injection pipe technique. This technique requires multiple sacrificial grout injection pipes or hoses, normally made from 2 inch, 3 inch or 4 inch (about 5 cm, 8 cm or 10 cm) diameter HDPE or PVC, that are successively placed along the length of the duct bank. Grout is pumped into the end of each grout pipe in turn until the space in the casing is filled with grout over the full length of the casing. When the space that is reached by one grout pipe is filled, the next pipe or hose is used until the entire space in the casing has been filled with grout.

A number of methods have been devised for organization and separation control of conduits for open cut trench concrete encased duct banks. Many of these methods are depicted in the following patents: U.S. Pat. Nos. 2,462,399; 2,686,643; 2,849,027; 2,937,833; 3,523,667; 3,643,005; 3,856,246; 3,964,707; 4,183,484; 4,244,542; 4,306,697; 4,601,447; 4,618,114; 5,104,072; 5,605,419; 6,076,863; and 6,375,017. These prior art spacers and concrete encased duct bank installation methods hold the conduits vertically and horizontally, but do not provide for longitudinal restraint, probably because these patents envision filling an open cut trench with concrete or grout from above, not from the side as would be the case in a closed casing or directionally-bored hole.

U.S. Pat. Nos. 5,137,306, 5,372,388, 6,076,863 and 6,711,328 depict conduits separated by spacers that are placed inside a casing. These patents related to very small conduits for fiber optic cables. Since fiber optic cables do not generate any heat, so no provision is made in these designs for placement of grout between the conduit outer diameter and the casing inner diameter. Finally, U.S. Pat. No. 7,806,629 discloses side-loading spacers which are also useful in guiding and holding conduits or ducts for underground installations. This patent is incorporated by reference into this document for all that it discloses.

What is needed is a better way of spacing and holding apart conduits for power and communications cables in underground or confined installations. The improved method should allow for controlled spacing and excellent heat conduction, while providing an efficient, economical, and easy way to install the conduits.

SUMMARY

One aspect of the disclosure is a spacer. The spacer includes a first spacer arm comprising a plurality of bores on a first side of the first spacer arm and at least one bore on a second side of the first spacer arm, the first spacer arm further comprising two transversely-mounted wheels on opposite ends of the first spacer arm, and also includes a second spacer arm comprising a plurality of bores on a first side of the second spacer arm and at least one bore on a second side of the second spacer arm, the second spacer arm further comprising two transversely-mounted wheels on opposite ends of the second spacer arm.

Another aspect of the disclosure is a spacer. The spacer includes a first spacer arm comprising a plurality of bores on a first side of the first spacer arm and at least one bore on a second side of the first spacer arm, the first spacer arm further comprising two transversely-mounted wheels on opposite ends of the first spacer arm; a second spacer arm comprising a plurality of bores on a first side of the second spacer arm and at least one bore on a second side of the second spacer arm; a third spacer arm comprising a plurality of bores on a first side of the third spacer arm and at least one bore on a second side of the third spacer arm, the second spacer arm further comprising two transversely-mounted wheels on opposite ends of the second spacer arm; and a fourth spacer arm comprising a plurality of bores on a first side of the fourth spacer arm and at least one bore on a second side of the fourth spacer arm. In this spacer, the first and the second spacer arms are assembled together with a plurality of fasteners to form a first half of the spacer and the third and the fourth spacer arms are assembled together with a plurality of spacer fasteners to form a second half of the spacer.

Another aspect of the disclosure is a spacer. The spacer includes a first spacer arm comprising a plurality of bores on a first side of the first spacer arm and at least one bore on a second side of the first spacer arm, a second spacer arm comprising a plurality of bores on a first side of the second spacer arm and at least one bore on a second side of the second spacer arm, and a third spacer arm comprising a plurality of bores on a first side of the third spacer arm and at least one bore on a second side of the third spacer arm, the third spacer arm further comprising two transversely-mounted wheels on opposite ends of the third spacer arm. The spacer also includes a fourth spacer arm comprising a plurality of bores on a first side of the fourth spacer arm and at least one bore on a second side of the fourth spacer arm, a fifth spacer arm comprising a plurality of bores on a first side of the fifth spacer arm and at least one bore on a second side of the fifth spacer arm, and a sixth spacer arm comprising a plurality of bores on a first side of the sixth spacer arm and at least one bore on a second side of the sixth spacer arm, the sixth spacer arm further comprising two transversely-mounted wheels on opposite ends of the sixth spacer arm. In this spacer, the first, second and third spacer arms are assembled together with a plurality of spacer fasteners to form a first half of the spacer and the fourth, fifth and sixth spacer arms are assembled together with a plurality of spacer fasteners to form a second half of the spacer.

Another aspect of the disclosure is a method of loading conduit into multi-part conduit spacers for placement into a casing, a tunnel or a longitudinal arcuate hole. The method includes steps of furnishing a plurality of multi-part conduit spacers, each multi-part conduit spacer comprising, a first spacer arm comprising a plurality of bores on a first side of the first spacer arm and at least one bore on a second side of the first spacer arm, the first spacer arm further comprising two transversely-mounted wheels on opposite ends of the first spacer arm, and a second spacer arm comprising a plurality of bores on a first side of the second spacer arm and at least one bore on a second side of the second spacer arm, the second spacer arm further comprising two transversely-mounted wheels on opposite ends of the second spacer arm. The method also includes steps of placing a first conduit into an assembly fixture, placing the first spacer arm atop the first conduit, assembling a first plurality of conduits atop the first spacer arm, assembling the second spacer arm to the first plurality of conduits, assembling a second conduit atop the second spacer arm, thus forming a bundle, and securing the bundle by banding an outside of the bundle.

There are many aspects for this disclosure, only a few of which are detailed herein.

DETAILED DESCRIPTION

The preparation and execution of underground grouting installations for power and communications cables is not something for the faint of heart. As described above, thousands of pounds of cabling, conduit and wire bundles must be securely and safely installed. Installations sometimes range into the thousands of feet. Grout is blindly and horizontally injected at a high pressure into a casing, such as a casing made or steel or other material, through at least many hundreds of feet, and as noted, sometimes a thousand feet or more from each side. A typical installation, showing the single end extractable grout injection pipe method of injecting grout, is depicted inFIG. 1A. Underground conduit site10includes casing11, typically between 12 and 48 inches (30 to 120 cm) in diameter, and now perhaps even up to 60 inches (150 cm) or more. A passage is dug into the ground and the casing is then placed into the ground. An assembly12of conduits16for several power or communications cables, or both, and a grout injection pipe, is then assembled to a plurality of spacers14, such as single-wall bore spacers, of which the term single-wall is explained below. The spacers are used to ensure minimum distances between conduits for power cables to allow for heat dissipation and also to minimize EMI/RFI interferences. The spacers are also used to support the grout pipe.

The conduits are typically mounted to the spacers and then held in place by fasteners or banding13placed around the cables or the spacers, or both. Grout18is injected by grouting pumps through a grout injection inlet17and pumped through grout pipes15. As noted, the grout may need to be pumped many hundreds of feet. The grout eventually reaches the area19downstream at the end of the grout pipe and fills the space in the casing11that is not otherwise occupied by conduits, or spacers.

FIGS. 1A and 1Bdepict two distinct prior art methods for filling casings with grout, the single end extractable grout injection pipe technique, inFIG. 1A, and the single end sacrificial grout injection pipe method inFIG. 1B.

The single extractable grout injection pipe technique, depicted inFIG. 1B, is accomplished by installing an injection pipe from the boring end of the casing to a point just a few feet short of the receiving end of the casing. The injection pipe is installed in the casing along with the conduits and bore spacers. The extractable grout injection pipe is supported by, but is not attached to the bore spacers. With this technique, the outer diameter of the extractable injection pipe must be smooth over its full length to ensure that it will ride without hindrance through and/or over the bore spacers. The injection pipe may be flush-coupled steel, lengths of steel pipe that have been welded together or a single continuous length of heavy wall HDPE pipe. Heavy wall PVC Conduit is on occasion used but the belled ends that are used to connect the sections of PVC conduit together cause a hindrance in the extraction.

Both ends of the casing are closed off or bulk headed. The conduits extend through closely fitted holes in the bulkheads. The grout injection pipe fits through an oversize hole in bulkhead located on the boring end of the casing. From the boring end of the casing, grout is pumped into the grout injection pipe. As the area between the conduit outer diameters and casing inner diameter is filled, the grout the injection pipe is withdrawn. The discharge end of the grout injection pipe is kept embedded in the grout slurry at all times to avoid air pockets. The grout is pumped through the injection pipe under sufficient pressure to fill all open spaces but not high enough to cause the conduits to collapse or pull apart. After the grout has hydrated and hardened, power cables or communication cables are pulled into the conduits.

The other generally-used technique is the single end sacrificial grout injection method, depicted inFIG. 1B. This method100is used on relatively long bores where the grout has to be pumped a long distance. Pumping grout through the sacrificial grout injection pipes help ensure that there are no grout voids and allows more time to fill the casing with grout. The single end sacrificial grout injection pipe method is accomplished by installing a multiple number of grout injection pipes102of varying lengths from the boring end104of the casing106to the receiving end108of the casing. The first injection pipe102ais installed at the boring end of the casing and goes directly into the casing. Additional injection pipes, each a shorter length than the last, are secured to the bore spacers along with the conduits and loaded into the casing. The injection pipes may be steel, heavy wall HDPE or heavy wall PVC and are normally 2 inches (5 cm) nominal to 4 inches (10 cm) nominal in diameter.

In this technique, both ends of the casing are bulk headed. The conduits and the grout injection pipes extend through closely fitted holes in the bulkheads. A vent103is placed at the top of the receiving end of the casing. Grout is pumped into the first injection pipe102auntil the far nozzle102bof the second injection pipe has been covered with grout. After the nozzle of the second injection pipe has been covered, the inlet to the first injection pipe is closed and grout is pumped into second injection pipe until the third injection pipe nozzle has been covered with grout. This sequence is repeated until grout discharges from the vent103located at the receiving end of the casing. The grout injection pipes are left in the casing and the grout is left to hydrate.

Both techniques require that the grout injection is a continuous, non-stop process. The reason that this injection method is known as the “single end sacrificial grout injection pipe method” is that the grout is pumped into the casing from one end only and the grout injection pipes are sacrificed in the process of pumping the grout into the casing. After the grout has hydrated, hardened, power cables or communication cables are pulled into the conduits. There a number of variations to these two grout injection methods. Almost all of the variations have one thing in common; they require some type of a grout injection pipe or pipes that are utilized similar to the methods described. To describe all of the grout injection methods and variations is beyond the scope of this detailed description.

Pumping the grout requires great forces and imposes heavy side loads on the spacers14. It follows that the spacers need to securely contain and mount the pipes and conduits of interest. The spacers are typically made from plastic and are relatively thin, typically ½ to ¾ of an inch (1.3 cm to about 1.9 cm) if they are fabricated from PVC or HDPE, and typically 3/16 to ¼ inch (0.48 cm to about 0.64 cm) if they are fabricated from steel, although some are as thin as ⅛ inch (0.32 cm) and others as thick as 1 inch (2.5 cm). As depicted inFIG. 1A-1B, one way to add strength to the spacers, and to help prevent horizontal movement, is to use them in pairs, i.e., as double-wall spacers, as shown. Instead of a single perforated sheet of plastic, spacers typically use two sheets that are substantially identical, the spacers secured to each other by bushings that space the sheets apart and simultaneously hold them together. This adds considerable stability to the spacers. The additional width in the direction of the conduits or cables helps prevent turning and bending, as well as longitudinal movement of the spacers. Keeping the spacers in place helps to ensure that the conduits have equal separation throughout the installation, and the power and communications cables suffer no deterioration.

Duct spacers or bore spacers according to the present disclosure are used in the underground installation depicted inFIG. 2. A tunnel has been bored in the earth5and a casing11, made of concrete, pipe or large-diameter conduit, is used to house a duct bank200. The duct bank includes the conduits shown, and also include a plurality of spacers201,202,203,204used to contain and protect the duct bank. Spacers201-202and spacers203-204each comprise a double-wall spacer, as will be described. Spacer201includes a lower half210and an upper half230. Each of the upper and lower halves include two wheels214mounted on the spacers. The lower half210nestles or supports first lower conduit or duct216and smaller conduits or ducts217,218. First half210also supports conduits219,220, which may be the same size as conduit216or may be different. Additional smaller conduits221,222rest atop supported conduits217,218and are snugged in by upper half230. The upper half230also nestles conduits219,220and supports final conduit240. Thus, the upper and lower halves210,230both cooperate to support conduits or ducts219,220. Once the duct bank200is assembled, banding250is used around the duct bank, conduits and spacers, to tie the duct bank together.

An exploded view of the double-wall spacers201-202is presented inFIG. 3. Front lower half210is seen to comprise three laminae,211,212,213, snugged together with fasteners243. Outer (front) lamina211is different from inner laminae212,213, because outer lamina211mounts wheels214on opposite sides of the lamina. As shown by angle A, the two wheels on lamina211are mounted at about 90° to each other. While a right angle of 90° is preferred, it has been found acceptable that the wheels, in an assembled duct bank, will function if the angles are from 80° to about 100°. Any particular lamina or bound group of laminae may be relatively inflexible and the wheels will remain at the angle fixed by the individual lamina. When combined with other spacers and ducts or pipes into a duct bank assembly, however, there can be variation among the four angles that combine to form a 360° assembly. These natural variances can be tolerated, so long as the individual angles are within the bounds of about 90°±10°, that is within the bounds of about 80° to about 100°.

In addition to the three laminae discussed, rear lower half210aincludes three additional laminae,213a,212aand211a, mounted as seen, with outer lamina211aalso mounted on the outside (backside) of the spacer. Additional laminae211a,212aand213aare identical with laminae211,212and213, that is, lamina211is identical to lamina211a, and laminae212,213,212aand213aare all identical in this embodiment. As noted above, the outer laminae,211and211a, are different because they are each adapted to mount wheel214. The laminae are held together with spacer bushings240and long-bolt fasteners241. Not all the spacer bushings can be seen inFIG. 3, but each double-wall spacer, in this embodiment, may have fourteen spacer bushings, seven each for the top and bottom halves,210,230.

Front upper half230is identical with lower half210, but is inverted in use, as shown. Front upper half230includes three laminae,231,232,233, while rear upper half230aincludes three laminae231a,232a,233a. Outer lamina231is different from inner laminae232,233, because outer lamina231mounts wheels214on opposite sides of the lamina. As shown by angle A, the two wheels on each lamina231are mounted at about 90° to each other. The two sets230,230amay each be held together with fasteners243, washers246and nuts or nylon locking nuts247. The washers may be lock-washers. The laminae are then assembled using spacer bushings240and long-bolt fasteners241. The wheels on each of the sets of laminae are mounted at about 90° to each other. In practice, the placement of the wheels on the periphery of the duct bank forms four angles that may vary between eighty degrees and one hundred degrees, rather than four ninety-degree angles.

The exploded view ofFIG. 4depicts a birds-eye view of how the many components of the double-wall spacer fit together. Front lower half210includes laminae211,212,213, and rear lower half210acontains their identical counterparts,213a,212a,211a. Outer laminae211and211amay each mount two wheels214on axles215, the axle mounted to the outer lamina. For the front upper half230, there are a first three laminae, including outer laminae231and inner laminae232,233. There is also a second set230aof three laminae, including outer lamina231aand two identical inner laminae232aand233a. The outer laminae,231,231aeach mount two wheels214on axles215mounted to the outer laminae. As noted previously, the two wheels on any given lamina are mounted at about a 90° angle to each other. There are thus four sets of laminae, upper laminae230,230aand lower laminae210,210a. The two sets of three laminae may be secured together with short bolts243, washers246and nuts or nylon locking nuts247. The double-wall spacer,201-202is then assembled using spacer bushings240(fourteen each) with long bolts241. Keeping the wheels perpendicular to each other ensures that the finished duct bank will be able to move forward and maneuver in its casing or conduit using its wheels when the duct bank is installed in the casing.

FIGS. 5A and 5Bdepict a duct bank500made with a single wall spacer according to the present disclosure.FIG. 5Adepicts duct bank500and single-wall spacer501in casing11. Single-wall spacer501includes a bottom half505and a top half511, the top half and the bottom halves each including two wheels503, the two wheels mounted at 90° to each other. The top and bottom halves505,511each include one lamina or more than one laminae, as described above in other embodiments. The single-wall spacer holds and spaces a plurality of ducts or conduits. In this embodiment, these include large conduits517,518(two each) of a first diameter and four small conduits519of a second, smaller diameter. While it may be easier to accommodate diameters that are equal, other embodiments of this disclosure may accommodate conduit diameters that are different. In general, the outer diameter of the duct bank will be set by the spacers and their wheels, which are always on the periphery of the spacers and thus on the periphery of the duct bank. The pipes or ducts are spaced so that their outer surfaces are not on the periphery, because these outer surfaces would interfere with movement of the duct bank within the casing. Thus, an outer diameter of the duct bank is set by the spacers and their wheels; the outer surfaces of the pipes or ducts on the periphery of the duct bank may also form a ducting or piping outer diameter, but this is always less than the outer diameter of the duct bank itself, which is set by the spacers and their wheels.

FIG. 5Bdepicts an exploded view of single-wall spacer501, which includes bottom half505and top half511. In this embodiment, the top and bottom halves are identical, except that their orientation is reversed for assembly into a duct bank. Bottom half505includes a first or bottom side506and an opposite or top side508. First side506includes a first bore507and opposite side508includes two bores509and two additional bores515. Bores507and509are adapted to accommodate a same size larger conduit, while bores515are adapted to accommodate smaller size conduits, which may be the same size or may be different sizes. Other combinations of bore sizes may be used. Wheels503on each half are intended to be oriented perpendicular to each other for easy travel through casing11. Top half511also includes two sides, first side512and opposite side514. First side512includes a first bore507and opposite side514includes two bores509and two additional bores515, in which bores507and509are adapted to accommodate a same size larger conduit, while bores515are adapted to accommodate smaller size conduits, which may be the same size or may be different sizes. More will be said later about vertical line of symmetry B.

Once the spacers are available, the duct bank may be assembled.FIGS. 6A-6Fdepict one way to assemble the duct bank using spacers according to the present disclosure.FIG. 6Adepicts a fixture600for holding a first duct or conduit601. A lower half602of a duct spacer, with wheels605, according to the present disclosure is then placed atop conduit601, so that a suitably-sized bore602aon the under-side of lower half602accommodates conduit601. InFIG. 6B, lower half602rests on fixture600and conduit601, while larger conduits603,604are placed into bores602b,602cof the lower half. In addition, smaller ducts606aare placed into bores602don the top side of lower half602. InFIG. 6C, additional smaller-diameter conduits606bare then placed atop conduits606a. When the assembly is steady, assembling then progresses toFIG. 6D. Here, a top half607of the duct spacer is added, with its underside bores602b,602cand602dfitting or accommodating already-installed conduits603,604,606b.

After top half607is added, an additional conduit608may be assembled into bore602a. Note that lower half602is identical to upper half607. Once assembly has been completed, as shown inFIG. 6E, banding611may be added to restrain the conduits and secure then in place. As shown inFIG. 6F, the duct bank610may then be wheeled into casing11using duct bank wheels605. Other embodiments of duct spacers or bore spacers may accommodate different sizes of ducts or conduits. As shown inFIGS. 7A-7B-7C, the duct bank610may then be installed in casing11. In this example, the earth5has been excavated or tunneled through, and casing11has been installed. The underground installation was evidently necessary to pass under a lake or river9.FIG. 7Ais an elevation view of the installation, whileFIG. 7Bdepicts a plan (top) view of the duct bank610using a double-wall spacer612. A cross-sectional view of the installation appears inFIG. 7C, depicting how the casing accommodates the double-wall spacer612, while the double-wall spacer accommodates and spaces four large conduits and four small conduits. In other situations, conduit of dissimilar sizes may be used.

A method80of assembling a duct bank and installing it is also part of the present disclosure, as shown in the flowchart ofFIG. 8. In one method, a bore spacer duct bundle is assembled, beginning by placing81a lower duct onto a fixture with a lower bore spacer, the lower side of the lower bore spacer accommodating the lower duct. This is the method depicted inFIG. 6A. After the lower duct and lower bore spacer have been placed, a first set of intermediate ducts is placed82atop the upper side of the lower bore spacer. PerFIG. 6B, this is the set of four ducts placed atop lower half602. After this first set of four ducts, a second set of two intermediate ducts is then placed83atop the first set of intermediate ducts. InFIG. 6C, these are the two small ducts606b. After these two ducts have been placed, the upper bore spacer is then placed84atop the two intermediate ducts, as shown inFIG. 5D, and then the top duct is placed85on top of the upper bore spacer. This forms a duct bundle or duct bank. The duct bank or duct bundle is then banded86, as shown inFIG. 6E. Finally, the duct bundle with its bore spacers is then wheeled or run87into the casing, perFIG. 6F. It is understood that there are many additional embodiments of the spacers depicted above, in which the top and bottom halves of the spacers are identical. Other spacers may include bores for different sizes and make-ups of conduits or ducts.

In another embodiment, the top and bottom halves of the spacers may be different, but the two halves nevertheless cooperate to bundle a plurality of ducts or conduits. One example is found inFIG. 9. A duct bank900comprises two double-wall spacers,901-902and903-904, which include single wall spacers901,902, snugged together with bushings and fasteners, and903,904, along snugged together with bushings and fasteners. Each single-wall spacer includes a bottom half910and a top half930. The top and bottom halves each include two wheels914mounted on opposite ends of each half, the two wheels oriented at about 90° to each other. Bottom half910rests upon larger conduit or duct916and smaller conduit or duct917, which interface with a first or bottom side of bottom half910. The opposite or top side of bottom half910nestles smaller conduits918,919. Bottom half top side also accommodates larger ducts920,921on opposite sides of the bottom half, as well as smaller duct922.

Top or upper half930also has two sides, a bottom side and a top or opposite side. When top half930is placed upon smaller conduits918,919, cut outs or bores on the bottom side nestle atop the smaller conduits918,919. The top half also nestles larger conduits or ducts920,921, again, on a first or bottom side of top half930. The opposite or top side of top half930accommodates a first smaller conduit923and also a second or larger conduit925within suitably-sized cut-outs or bores of the top half930. Additional bores accommodate two smaller conduits924,927. Altogether, the assembled bore spacer901, with top and bottom halves910,930, help to bundle four large conduits and seven smaller conduits. Manufacturing and tooling are easier if the four large conduits are all the same size or diameter, and this also holds if the seven smaller conduits are all the same size or diameter. However, the spacers may be designed for differently-sized ducts or conduits.

A more detailed view of the double wall spacer901-902presents inFIG. 10. Spacer901, the front portion ofFIG. 10, includes a bottom or lower half910and an upper half930; spacer902, the back portion ofFIG. 10, also includes a bottom or lower half910aand a top half930a. Front spacer901and back spacer902are joined by spacer bushings940and fasteners941,943, washers946and nuts947, such as nylon locking nuts. Lock washers or other locking fasteners may be used. Each bottom half910,910aincludes four laminae,911,911,912,913, or913a,912a,911a,911a. Bottom halves910,910aeach include two of outer lamina911or911a(second outer rear lamina911anot visible inFIG. 10), since this lamina lacks a central portion. In addition, note that lamina911is additionally different from laminae912,913. Each of the two front laminae911have provisions for mounting a wheels914. When the wheels are mounted to each one the two wheels will be at right angles to each other for rolling along the sides of the casing into which the duct bundle is placed. The same holds true for rear laminae911a. Front laminae911are also different because they lack a central portion and thus lack bores in the middle1108cwhich are present in laminae912,913(seeFIG. 12B). When the spacers901-902are joined to form a double-wall spacer, the order of the laminae are reversed. Thus, in back half lower portion910a, the two laminae911a, very similar to laminae911, also each mount a wheel914, so that the two wheels914so mounted, are also perpendicular to each other, and are on the backside, that is the out-side of the double-wall spacer901-902. The two laminae,911and911aare identical except for the mounting of the wheel914. Front laminae911may have a front slot cut into them for mounting an axle for the wheel. If front lamina911were to be mounted in the place of rear lamina911a, the slot would face lamina912aand would not face the outside (the rear side) of spacer902. This is a very subtle difference. Even though laminae911and911aare very similar, the slot would not be the same. Thus, laminae911and911aare very similar but are not identical. It is fair to say that laminae911and911aare substantially similar.

This also holds for the upper halves930,930a. Front upper half930includes four laminae, two front laminae931and internal laminae932,933. Rear upper half930aalso includes four laminae, rear outer lamina931a(second outer rear lamina not visible inFIG. 10) and internal laminae932a,933a. Laminae931and931aare almost identical, as discussed above for laminae911and911a. A slot on the outside of the laminae will be on a front face of laminae931and on the opposite face of rear lamina931a. Internal laminae932,932a,933and933aare identical. Note that lamina931is additionally different from laminae932,933. Each front lamina931(and rear lamina931a) has provisions for mounting a wheel914. When the wheels are mounted to the two laminae,931-931or931a-931a, the wheels will be oriented at right angles to each other, for rolling along the sides of the casing into which a duct bundle is placed. Front lamina931(and rear lamina931a) are also different because they lack a central portion and thus lack bores1116cin the middle which are present in laminae932,933(seeFIG. 12B). The two sets of laminae930,930amay each be held together with fasteners943, washers946and nylon locking nuts or nuts947. The washers may be lock-washers, and other hardware may be used. The two sets930,930aare then assembled using spacer bushings940and long-bolt fasteners941. The wheels on each of the sets of laminae are mounted at about 90° to each other.

The exploded view ofFIG. 11depicts a birds-eye view of how the many components of the double-wall spacer fit together. The exploded view includes front and rear spacers901,902, and includes their lower halves910,910aand upper halves930,930a. Front lower half910includes laminae911(two each of lamina911),912,913, while rear lower half910aincludes their substantially identical or identical counterparts,913a,912a,911a(two each of lamina911a, only one visible in theFIG. 11). Outer laminae911and911amay each mount a wheel914on an axle915, the axle mounted to the outer laminae,911,911a. When mounted, the two wheels on laminae911-911and on laminae911a-911awill be perpendicular to each other. For the front upper half930, there are also four laminae, including two outer laminae931and two inner laminae932,933. Rear upper half930aalso includes a set of four laminae, including two outer lamina931aand two identical inner laminae932aand933a. The outer laminae,931,931aeach mounts wheel914on an axle915mounted to the outer lamina. Bushings948and end caps949may also be used to mount the axles and wheels. As noted previously, the two wheels on any given set of the outer laminae are mounted at about a 90° angle to each other. The two sets of four laminae may then be secured together with short bolts943, washers946and nuts947. The double-wall spacer is then assembled using spacer bushings940(ten each) with long bolts941. Keeping the wheels perpendicular to each other ensures that the finished duct bank will be able to move forward and maneuver in its casing or conduit when the duct bank is installed in the casing.

As noted above, any particular lamina or bound group of laminae in this embodiment may be relatively inflexible and the wheels will remain at the angle fixed by the individual lamina or laminae, that is, at a 90° angle. When combined with other spacers and ducts or pipes into a duct bank assembly, however, there can be variation among the four angles that combine to form a 360° duct bank assembly. These natural variances can be tolerated, so long as the individual angles are within the bounds of about 90°±10°, that is within the bounds of about 80° to about 100°. In this embodiment, for example, the angles of the two911laminae in bottom half910will be fixed by their assembly into a group that also involves laminae912,913. This also holds true for the two931laminae of top half930, and likewise for bottom half910aand rear upper half903a. When combined into double-wall spacer901-902, however, the four angles about the periphery may vary from a desired 90° angle by as much as ±10 degrees.

FIGS. 12A and 12Bdepict a duct bank1100made with a single wall spacer according to the present disclosure.FIG. 12Adepicts a single-wall spacer1101in casing11. Single-wall spacer1101includes a bottom half1105and a top half1111, the top half and the bottom half each including two wheels1103. The top and bottom halves1105,1111each include one lamina or more than one laminae, as described above in other embodiments. The single-wall spacer holds and spaces a plurality of ducts or conduits. In this embodiment, these include large conduits1116,1120,1121,1127of a first larger diameter, or more than one diameter. The spacer also holds several smaller conduits1117,1118,1119,1122,1123,1124,1125of a second, smaller diameter, or of a variety of smaller diameters. While it may be easier to accommodate diameters that are equal, other embodiments may accommodate conduit or ducts having diameters that are different from one another. Note the four ninety-degrees angles shown between the wheels. In practice, each of these may vary from eighty degrees to one hundred degrees, with the total angles around the periphery of the duct bank always summing to three hundred sixty degrees.

In general, the outer diameter of the duct bank1100will be set by the spacers and their wheels, which are always on the periphery of the spacers and thus on the periphery of the duct bank. The pipes or ducts are spaced so that their outer surfaces are not on the periphery, because these outer surfaces would interfere with travel of the duct bank through the casing. Thus, an outer diameter of the duct bank is set by the spacers and their wheels; the outer surfaces of the pipes or ducts on the periphery of the duct bank may also form a ducting or piping outer diameter, but this is always less than the outer diameter of the duct bank itself, which is set by the spacers and their wheels. Note the dis-symmetry shown inFIG. 12A—the four 90° angles and their coordinate system center on the assembled duct bank, not on the casing. On the bottom of the duct bank, wheels1103make contact with the inner diameter of the casing11, while pipes or ducts, such as1116,1117,1120and1122do not make contact with the casing.

FIG. 12Bdepicts an exploded view of single-wall spacer1101, which includes bottom half1105and top half1111, each of which may comprise several laminae or layers. In this embodiment, the top and bottom halves are not identical because of differences in the middle portions, as will become apparent. In addition, their orientation is reversed for assembly into a spacer and into a duct bank. Bottom half1105includes a first (bottom) side1106and an opposite (top) side1108. First side1106includes a first bore1106a, for a larger diameter conduit or duct and a smaller bore1106bfor a smaller diameter duct. Opposite side1108includes five bores. These include first larger bore1108aand second larger bore1108b, and also includes three additional smaller bores1108cin the left side and center of the top side. Bores1108aand1108bare adapted to accommodate larger size conduits, which may be the same size or may be different sizes. Bores1108care adapted to accommodate smaller size conduits, which may be the same size or may be different sizes. Other combinations of bore sizes may be used. Wheels1103on each half are intended to be oriented perpendicular to each other, see Angle A, for easy travel through casing11. Top half1111also includes two sides, first (top) side1112and opposite (bottom) side1116. First side1112includes a first smaller bore1112a, a second smaller bore1112band a larger-size bore1112c. Bottom or opposite side1116includes two larger-size bores1116aand1116band also includes space for two additional smaller-sized bores1116c, spaced closely together, and a third smaller-sized bore1116d. Bores1116a,1116band1112care sized to accommodate a same size larger conduit, while bores1112a,1112b,1116cand1116dare adapted to accommodate smaller size conduits, which may be the same size or may be different sizes. Note how bores1108aand1116bcooperate to hold a single larger-sized conduit; bores1108band1116aalso cooperate to hold a single larger-sized conduit. Other combinations of bore sizes may be used.

Once the spacers are available, the duct bank may be assembled.FIGS. 13A-13Hhelp visualize how the assembly is accomplished. An assembly fixture1300may be useful. A first conduit1301and a second smaller conduit1302are placed into fixture1300, as shown inFIG. 13A. A lower half1305of a single-wall spacer, with wheels1305a,1305bis then placed atop the conduits1301,1302, using the appropriate bores on the first or bottom side of the spacer for the conduits, perFIG. 13B. As then shown inFIG. 13C, two smaller conduits1303are then placed into the second or opposite side of the spacer lower half. As then shown inFIG. 13D, the top or upper half1311of the single-wall spacer, with wheels1305c,1305dis then placed atop conduits1303. This places the first or bottom side of spacer1311in contact with conduits1303. Side assembly of a plurality of conduits is then possible, as shown inFIG. 13E. The top side of lower half1305is adapted to accept conduit1306and the bottom side of upper half1311is adapted to accept conduit1306a. As also shown inFIG. 13E, top and bottom halves1311,1305cooperate to accept larger-diameter conduits1304,1304a. At least larger conduits1304,1304amay require some additional fixture or help to remain in place before banding takes place. Smaller conduit1308is then placed into the upper side of the upper or top half1311, followed by larger-diameter duct or conduit1309aand smaller-diameter conduit1309b, as shown inFIG. 13F. The duct bank1315is then formed by securing the spacers and conduits with banding1313, shown inFIG. 13G. Finally, the duct bank1315is rolled into casing11using the assembled duct bank and the wheels1305a,1305b,1305c,1305dof the spacers. Other embodiments of duct spacers or bore spacers may accommodate different sizes of ducts or conduits.

As shown inFIGS. 14A-14B-14C, a duct bank1415may then be installed in casing11. Duct bank1415may be a double-wall version of duct bank1315using double-wall spacers1412instead of the single-wall spacers used for duct bank1315. In this example, the earth5has been excavated or tunneled through, and casing11has been installed. The underground installation was evidently necessary to pass under a lake or river9.FIG. 14Ais an elevation view of the installation, whileFIG. 14Bdepicts a plan view of the duct bank1415using a double-wall spacer1412. The cross-sectional view of the installation appears inFIG. 14C, depicting how the casing accommodates the double-wall spacer1412, while the double-wall spacer accommodates and spaces four large conduits and seven small conduits. In other situations, conduit of dissimilar sizes may be used.

A method150of assembling a duct bank and installing it is also part of the present disclosure, as shown in the flowchart ofFIG. 15. In one method, a bore spacer duct bundle is assembled, beginning by placing151two lower ducts onto a fixture with a lower bore spacer152, the lower side of the lower bore spacer accommodating the lower two ducts, which may be the same size or may be different sizes, as shown inFIG. 13A. This is the method depicted inFIGS. 13A-13B. After the lower ducts and lower bore spacer have been placed, a first set of intermediate ducts is placed153atop the upper side of the lower bore spacer, as shown inFIG. 13C. The next step is to place154the upper bore spacer onto the first set of intermediate ducts, as shown inFIG. 13D. Then both outer sets of intermediate ducts are placed155between the upper and lower bore spacers, followed by placing156the upper ducts onto the upper bore spacer, as shown inFIGS. 13E-13F. This completes the components of the duct bundle or duct bank, at least for the portion of the ducts concerned with this particular spacer. The bundle is then banded157, both sides, top and bottom, and wheeled158into the casing, using the wheels of the duct bank to traverse the sides of the casing. This is depicted inFIGS. 13G-13H.

As a rule, single wall spacers are more useful for smaller casings, such as those used for straight bores of 42 inches (107 mm) and smaller diameters. If the diameter is greater than 42 inches (107 mm) or if the bore is a directional bore, double-wall spacers should be used. As is clear, the double-wall spacers add a great deal more dimensional stability than a duct bank constructed with single-wall spacers is capable of. The conduits used may include rigid PVC, commercially available in diameters from about 1 inch to 12 inches (25 mm to 300 mm). Other options include HDPE, in diameters from 1 inch to 6 inches (25 mm to 150 mm) and fiberglass, from about ¾ inches to about 8 inches (20 mm to 200 mm). Other conduits may be used.

Spacing between halves of double-wall spacers may be as desired. For example, a distance of about 3-4 inches (about 8-10 cm) works well for dimensional stability during assembly, and for handling ease of the finished duct bank. Other distances may be used as desired. The introduction above to casings and spacers noted that grout may be used to embed a duct bank and protect the ducts and the duct bank. Note that the central portion of the duct bank described above, e.g.,FIGS. 7C and 14C, have voids that allow grout to flow through the spacers. For example, inFIG. 7C, the central portion, with spaces between the four small conduits, will allow grout to flow through—see alsoFIG. 5A. InFIG. 14C, there are gaps at least on the periphery between the outer banding, the larger conduits and the smaller conduits—for this, seeFIG. 12A.

This disclosure of multi-part bore spacers has many embodiments in addition to the few described herein. For instance, the spacers have been described and shown as routed from thermoplastic sheet materials, while they may be fabricated or molded from other materials, such as thermoset materials, wood, or other natural materials. Good shop practices should be observed when fabricating spacer and spacer laminae, for example, all corners should be rounded or radiused, including internal as well as external corners. Sharp edges should also be smoothed or beveled. This helps to avoid stress concentrators and contributes to longer lives for the spacers and the duct banks into which they are made. The spacers disclosed herein are different in that they have no center as such, and also have no top or bottom as such, in contrast to spacers according to the prior art. In the spacers disclosed herein, the conduits or ducts themselves occupy significant portions of the outer periphery of the duct banks.

The spacers disclosed herein also have unique symmetry, in that at least the peripheral portions of the spacers tend to have radial symmetry, wherein the central portions may have more variance. Thus, the spacers505,511inFIG. 5Bhave 180-degree radial symmetry, reflective symmetry, since the top and bottom portions of the spacer are identical. In addition, each spacer itself has reflective symmetry, in that the left-and-right halves of the spacers505,511are also equal, as shown by reflective line-of-symmetry B. In contrast, the spacers901,902inFIG. 10lack 180-degree symmetry because their central portions are not identical; note however, that the outer portions of the spacer, those defined by outer laminae911, have symmetry, and indeed have a higher degree of symmetry, ninety-degree symmetry, since there are four substantially identical laminae in this construction.

The laminated reinforcements discussed above may retain axles for the wheels, but other reinforcements may be used and other devices provided in order to add reinforcements or wheels to the side-loading separators. For instance, metal or reinforced plastic shoes may be placed on ends of the arms and pinned in place by transverse pins in the arms. Bushings and fasteners have been described as providing ways to secure additional horizontal stability to the top-and-bottom spacer combinations, but there are additional ways to add stability to the assemblies. For instance, joining side-arms with additional securing points may be used. It is also possible to join two spacers with a fixed horizontal spacing by using clamps with flanges on the out-sides of both spacers. Such clamps could use fasteners through orifices in the clamps and the spacers, or could alternatively use latches that fasten on raised bosses or other surfaces of the spacers. The process has been described as loading conduits into spacers because this is the commercial practice, with the actual power or communications cables later pulled into the conduits. The process would also work if the cables themselves were assembled onto the spacers. The cables are much heavier than empty conduit, but assemblies with cables and the spacers described herein are also possible.