Abstract:
Conduit spacers useful in preparing duct banks are disclosed. The conduit spacers are designed for attachment to each other in vertical and horizontal combinations, that is, they may be arranged in side-by-side arrays, up-and-down arrays, or arrays that are both side-to-side and up-and-down. Thus, the conduit spacers include both vertical and horizontal restraints or interlocks. The vertical interlocks are achieved by the use of tapered tabs and tapered slots, both the tabs and the slots having tapers in the same horizontal direction. Horizontal interlocks are made by the use of rails and matching grooves in the sides of the spacers. Thus, both vertical and horizontal interlocks are achieved by assembling the ducts in a horizontal direction, side-by-side as desired for width, and up-and-down as desired for height. The number and length of conduits and the length of the duct banks needed dictate how many spacers are needed.

Description:
TECHNICAL FIELD 
     The technical field is that of spacers for separating and supporting power and communication conduits in underground trenches before and during the concrete pour. 
     BACKGROUND 
     Cables for electric power, control 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 other structures. Conduits, also called ducts, run underground for such cables should be parallel to each other and spaced apart from each other in a controlled manner in order to minimize any electrical interference. This spacing also acts to dissipate the heat generated by transmission of electric power and electric signals in the cables. In addition, the conduits and cables should be protected, primarily from digging, whether with hand tools or with mechanized equipment, such as backhoes. 
     A trench may be dug and conduits placed into the trench at a distance from each other. For example, a series of conduits may be placed side-by-side in the bottom of the trench and separated from each other by removable spacers. Once the conduits are placed, the spacers may be removed and all space between the conduits filled with earth, sand or concrete. Thus, the space is filled with thermally conducting but electrically insulating material. If there are to be several vertical layers of conduits, this procedure is very inefficient and time-consuming. In another prior art method, spacers are made with large teeth in the general form of a rake to define spaces between conduits. These spacers may then be used to organize and separate the conduits. However, maintaining vertical separation may be challenging with this method. 
     It is important to fill all the spaces between the conduits no matter which technique is used to space them apart. It is difficult to accomplish this when the conduits are in several vertical layers. The filler material ideally should be a flowable material, i.e., a material that flows freely downward and sideways in all directions when dispensed into the trench. A more-flowable filler material consists of 50 to 100 lb (about 23 to about 45 kg). Portland cement, 2750 lb (about 1250 kg) of fine sand, and 500 lbs. (about 227 kg) water (maximum) per cubic yard (about 0.765 cubic meters), having a 28-day compressive strength of 50-150 psi (about 0.34 MPa-about 1 MPa). A heavier but still flowable filler material includes a normal weight concrete mix with Portland cement, aggregate having a maximum size of ⅜ inch (about 9-10 mm), and sand and water. The heavier material has an 8 inch (about 203 mm) minimum slump and a 28-day compressive strength of 3000 psi (about 21 MPa). The ability to spread and fill the entire space is needed for good heat transfer and thermal conductivity. 
     One way to insure even spacing between conduits for power and communications cables is to fabricate banks of ducts which are separated by conduit spacers. The duct banks are then encased in concrete or other material as described above. After the concrete has hydrated or set, cables are pulled through the conduits. The concrete provides a heat transfer medium for conducting heat to the surface, normally the ground surface, and also protects the cables from moisture, rodents and any contractors attempting to dig in the immediate vicinity of the duct bank. 
     Fabrication of a duct bank typically requires preparing an assembly of conduits and spacers in a trench and then encasing the duct bank in concrete. One method of assembling the spacers is to simply place conduits into bores prepared in a first layer of one or more spacers, and then to place additional spacers and conduit atop the bottom layer. A sturdier assembly may be made by positively locking the conduits into the spacers and by locking the spacers themselves together. Spacers typically do not have easy and reliable ways to interlock to each other. 
     For example, U.S. Pat. No. 4,601,447, depicts conduit spacers with vertical interlocks made of snap-fit joints, with male snap-fit joints facing downward and female snap-fit joints facing upward. The snap-fits mate when the parts are assembled one-to-another vertically. Molding these snap-fit joints requires very tight tolerances on the tooling if the joints are to work and not interfere with assembly. In addition, the arced portion of the spacer, the portion in which the conduit rests, is relatively narrow and may not provide a sturdy and balanced support for a loaded conduit. 
     In another example, Snap-Loc spacer model SP4W20-2, made by the Carlon Co., Cleveland, Ohio, U.S.A., has slots well above the bottom of the spacer and tabs near the top of the spacer. The tabs are tapered with the narrow portion facing the feet and with the wide portion on the opposite site. The slots are also tapered; however, they are tapered in the opposite direction, with the wide portion on the feet side and with the narrow portion on the opposite side. This may be a result of the tooling used. Thus, when spacers are assembled together, it is more difficult to make the assembly because the tapers are opposed; once assembled, the resulting joint is loose. Of course, the spacers may be assembled with the tapers made in the same direction; if this done however, the vertical interlocks (feet) will face in opposite directions, and the spacers must be alternated in every layer or tier. This amount of detail is very difficult to accomplish in field situations. Even when this is accomplished, however, the fit is very loose and the assembly is not tight or strong. A five-page brochure on these spacers is included in an Information Disclosure Statement accompanying this patent and is hereby incorporated by reference in its entirety. 
     What is needed is a better conduit spacer suitable for assembly with matching conduit spacers to form a tight, coherent duct bank. These conduit spacers should be easy to assemble and should not require expensive or hard-to-manufacture tooling with very tight tolerances. 
     BRIEF SUMMARY 
     One embodiment is a conduit spacer. The conduit spacer includes a base having generally planar portions and having at least one contiguous convex portion adjacent the generally planar portions, at least two stacking slots connected to the base and on left and right sides of the base, each stacking slot having a taper in a general first direction (back to front or front to back) of a width of the base. The conduit spacer also includes at least one generally U-shaped body supported above the base, each U-shaped body having an open end extending away from said base and stacking tabs extending from both ends of each U-shaped body, said stacking tabs having a taper in a same general first direction (back to front or front to back) of a width of the base. 
     Another embodiment is a conduit spacer. The conduit spacer includes a base comprising generally planar portions and at least two stacking slots connected to the base and on left and right sides of the base, each stacking slot having a taper in a general first direction (back to front or front to back) of a width of the base, wherein a narrower end of each stacking slot is blind and a wider end of each stacking slot is open. The conduit spacer also includes at least one generally U-shaped body supported above the base, each U-shaped body having an open end extending away from said base and stacking tabs extending from both ends of each U-shaped body, said stacking tabs having a taper in a same general first direction of a width of the base. 
     Another embodiment is a conduit spacer. The conduit spacer includes a base having generally planar portions and having at least one contiguous convex portion adjacent the generally planar portions and at least two stacking slots connected to the base, on left and right sides of the base, and opening to a bottom surface of the base, each stacking slot having a taper in a general first direction (back to front or front to back) of a width of the base. The conduit spacer also includes at least one generally U-shaped body supported above the base, each U-shaped body having an open end extending away from said base and stacking tabs extending from both ends of each U-shaped body, said stacking tabs having a taper in a same general first direction of a width of the base. 
     Yet another embodiment is a conduit spacer. The conduit spacer includes a base having generally planar portions and having at least one contiguous convex portion adjacent the generally planar portions, at least one generally U-shaped body supported above the base, each U-shaped body having an open end extending away from said base, stacking tabs extending from both ends of each U-shaped body, and stacking slots connected to the base and on left and right sides of the base, each stacking slot having a length greater than a length of each of the stacking tabs. 
     Another embodiment is a conduit spacer. The conduit spacer includes a base having generally planar portions and having at least one contiguous convex portion adjacent the generally planar portions and at least one generally U-shaped body supported above the base, each U-shaped body having an open end extending away from said base. The conduit spacer also includes at least two stacking tabs extending from ends of each U-shaped body and at least two stacking slots connected to the base and on opposite sides of the base in a direction perpendicular to a width of the base, each stacking slot further comprising an angled lead-in section. 
     Another embodiment is a method of assembling a duct bank. The method includes steps of furnishing at least two conduit spacers, each conduit spacer including a base having generally planar portions and having at least one contiguous convex portion adjacent the generally planar portions and at least two stacking slots connected to the base and on left and right sides of the base, each stacking slot having a taper in a general first direction (back to front or front to back) of a width of the base. Each conduit spacer also includes at least one generally U-shaped body supported above the base, each U-shaped body having an open end extending away from said base and stacking tabs extending from both ends of each U-shaped body, each stacking tab having a taper in a same first direction (back to front or front to back) of a width of the base. The method then includes steps of joining the at least two conduit spacers to form an assembly by inserting the at least two stacking tabs of a first of the at least two conduit spacers into the at least two stacking slots of a second of the at least two conduit spacers, such that a front face of each of the at least two conduit spacers faces in a same direction and a rear face of each of the at least two conduit spacers faces in an opposite direction. 
     Another embodiment is an end cap for a conduit spacer. The end cap includes a top surface, a bottom surface opposite the top surface, an outer surface connecting the top and bottom surfaces, and an inner surface adapted to form at least a partial interface with a conduit. The end cap also includes at least one male connector or at least one female connector proximate the inner surface, wherein the at least one male or female connector is adapted for engagement with a corresponding female or male connector of the conduit spacer. In one embodiment, the end cap is useful as a distance gage, wherein the end cap and the distance are adapted for use as a distance gage to control a thickness of a filler or concrete. In one embodiment, the open side is adapted for enclosing a circumference of a conduit between the end cap and the conduit spacer. 
     Other embodiments and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are meant to be illustrative rather than limiting. In the drawings: 
         FIG. 1  depicts a perspective view of a duct bank installation with an embodiment of a duct bank and spacers described herein; 
         FIG. 2  depicts a perspective view of a first embodiment of a conduit spacer depicted in  FIG. 1 , with end caps shown removed for clarity; 
         FIG. 3  depicts a perspective view of a second embodiment of a conduit spacer depicted in  FIG. 1  with end caps shown assembled to the conduit spacer; 
         FIG. 4  depicts an assembly of the conduit spacers of  FIGS. 2 and 3 ; 
         FIG. 5  depicts a front view of a stack of spacers as shown in  FIG. 2 , 
         FIG. 5A  depicts a closer view of the tabs of the spacers depicted in  FIG. 5 ; 
         FIGS. 6 and 6A  depict an inverted front perspective view of the spacer of  FIG. 2 , with a closer perspective view of the tab depicted in  FIG. 6A ; 
         FIGS. 7 and 7A  depict bottom, rear perspective views of the spacer of  FIG. 2 , with  FIG. 7A  depicting a closer view of the bottom and slot portion of the spacer; 
         FIG. 8  depicts a rear perspective view of a duct bank with the stacked spacers of  FIGS. 2 and 5 ; 
         FIGS. 8A and 8B  depict a closer view of the assembly of a tab of a bottom spacer being inserted into a slot of a top spacer in the duct bank; 
         FIG. 9  depicts a rear view of another embodiment of a duct bank assembly with stacked duct bank spacers; 
         FIGS. 9A-9D  depict closer and cross-sectional views of the assembly of a tab of a first spacer into a slot of a second spacer; and 
         FIGS. 10A-10D  depict closer and cross-sectional views of the assembly of a tab of a first spacer into a slot of a second embodiment of a spacer; 
     
    
    
     While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. The intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     A first embodiment of a duct bank with the spacers described herein is presented in  FIG. 1 . The installation  1  includes a duct bank  2  which has been placed in a trench  3  and then encased in protective concrete  4 . After the concrete cures, the installation is backfilled with the overburden or earth  5  that was previously removed. Duct bank  2  includes a bottom conduit spacer  20   a , holding two large conduits  6  and three smaller conduits  7 . A second conduit spacer  20   b  is mounted directly above, i.e., stacked and interlocked, atop bottom conduit spacer  20   a . As will be detailed later, conduit spacers  20   a ,  20   b  are vertically interlocked and can only be disassembled intentionally. Conduit spacer  20   b  sits atop the two large conduits mounted in conduit spacer  20   a . Conduit spacer  20   b  also mounts two large conduits  6  and three small conduits  7 . Coordinate axes for reference are depicted in  FIG. 1 , with axis Z along a width of the spacers or a length of the duct bank, axis X along a front face or length of the spacers, that is, along a width of the duct bank, and axis Y along a height of the spacers or duct bank. 
     (Conduit spacer  20   c  also mounts two large conduits  6  and three small conduits  7 . In one embodiment, the large conduits are 150 mm (about 6 inches) and the small conduits are 56 mm (about 2.2 inches). Conduit spacer  20   c  is staggered away from conduit spacers  20   a ,  20   b , thus avoiding a shear plane, much as masons stagger bricks when they build a wall. Top conduit spacer  20   d  is staggered away from conduit spacer  20   c  and is mounted upside down. The height from the center-top of the large conduits  6  to the top of the inverted spacer  20   d  is about 3 inches (about 75 mm). The spacers also include end caps  40 , explained below. 
     An inverted spacer may act as a concrete gage, in that when the concrete is poured so that it covers the top conduit spacer  20   d , there is a minimum distance of about 70-90 mm (about 2.7 inches to about 3.5 inches) of concrete covering the larger conduits. In one embodiment, for nominal 6-inch (150 mm) conduit, with 3 in (76 mm) horizontal and vertical spacing, a distance from the bottom of the spacer to the bottom of the inside of the U-shaped body, is about 121 mm (about 4.75 inches), or less. This insures an adequate amount of concrete at the base of the duct bank while not requiring an excess of concrete, such as allowed by conduit spacers that allow a larger gap. Table 1 below lists the maximum distance from the spacer bottom, or bottom of the spacer base, to the bottom inside of the at least one U-shaped body, for a series of spacers and conduit separations. 
     
       
         
               
             
               
               
             
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 MAXIMUM DISTANCE FROM SPACER BOTTOM TO 
               
               
                 INSIDE BOTTOM OF U-SHAPED BODY 
               
             
          
           
               
                   
                 Horizontal and Vertical Distance between conduits, 
               
               
                   
                 also known as conduit separation 
               
             
          
           
               
                 CONDUIT SIZE 
                 1.500 IN (38 MM) 
                 2.000 IN (51 MM) 
                 3.000 IN (76 MM) 
               
             
          
           
               
                 Nom. 
                 Actual 
                 Actual 
                 Distance, 
                 Distance, 
                 Distance, 
                 Distance, 
                 Distance, 
                 Distance, 
               
               
                 dia, in. 
                 od, in. 
                 od, mm 
                 in. 
                 mm. 
                 in. 
                 mm 
                 in. 
                 mm 
               
               
                   
               
             
          
           
               
                 2 
                 2.375 
                 60.33 
                 — 
                 — 
                 3.062 
                 78 
                 4.000 
                 102 
               
               
                 3 
                 3.500 
                 88.90 
                 — 
                 — 
                 3.250 
                 83 
                 4.188 
                 106 
               
               
                 4 
                 4.500 
                 114.3 
                 3.188 
                 101 
                 3.438 
                 87 
                 4.375 
                 111 
               
               
                 5 
                 5.563 
                 141.3 
                 — 
                 — 
                 3.625 
                 92 
                 4.562 
                 116 
               
               
                 6 
                 6.625 
                 168.3 
                 — 
                 — 
                 3.812 
                 97 
                 4.750 
                 121 
               
               
                 8 
                 8.625 
                 219.1 
                 — 
                 — 
                 4.000 
                 102 
                 4.938 
                 125 
               
               
                   
               
               
                 Interpolate table for conduit sizes and conduit separations not shown. 
               
             
          
         
       
     
     The conduit spacer  20  depicted in  FIG. 1  is shown in greater detail in  FIG. 3  and a simpler version of a conduit spacer  10 , for a single conduit, is depicted in  FIG. 2 . Conduit spacer  10  includes a base  12  with flats  13  or flat portions on either end and an arcuate or curved portion  14  in the center of the base  12 . The arcuate portion is convex, i.e., shaped like an outside of a sphere and in one embodiment, comprises about 90 degrees of arc of a circle. The bottom portion also includes slots  15 , not visible in this view, formed within bosses  16 . The upper portion includes a central generally U-shaped body  17 , which is concave, shaped like an inside of a sphere or bowl, and forms about 270 degrees of a circle. The ends of the U-shaped body include transition portions  18  and end tabs  19 . The slots  15  and tabs  19  are discussed below. In this embodiment of a spacer for a single conduit, there are slots  15  on the left and right sides of the base and tabs  19  on the left and right sides of the U-shaped body  17 . 
     The U-shaped body at rest is biased slightly inward at the top from what would be 270° of a perfect circle or cylindrical shape. This inward bias creates a snap-fit, so that when a conduit with a circular cross section is inserted into the body, the end portions or arms of the U-shaped body positively retain the conduit. The U-shaped body  17  forms the central part of the support structure for the conduit. Spacer  10  also includes adjacent support sections  38  to form a wider support base. The central portion of the U-shaped body is supported by a vertical rib  28  and may also be supported by side ribs  32 . The side ribs may be vertical or they may be angled somewhat from the vertical, as shown. 
     Lateral sides of the U-shaped body  17  are also supported by side buttresses  34 . The left and right sides of spacer  10  form respectively male and female joining portions, with arc portions  22  and tabs  24  or slots  26  for engagement with an additional spacer or with respective female or male end caps  40   a ,  40   b.    
     Female end cap  40   a  includes two arc portions  42 , a central portion  48 , and slots  46  for receiving engaging tabs  44  from male end cap  40   b  or from another spacer. Male end cap  40   b  also includes arc portions  42  and a center portion  48 . The arc portions  42  form a generally semicircular shape for accommodating within center portion  48  an additional, usually smaller, conduit than the conduit accommodated in the U-shaped body  17 , when connected to conduit spacer  10  or  20 . As best seen in  FIGS. 2 and 8 , the arc portions  42 , with arc portion  22  of spacer  10  or spacer  20 , form a generally circular shape for accommodating the smaller conduit  7 . 
     The end cap embodiments shown are generally in the shape of a semicircle or a capital letter C, with a closed side and an open side. The tabs extend outward from and are adjacent to the top and bottom sides in male end cap  40   b . The slots extend inward and form part of the top and bottom sides in female end cap  40   a . The top and bottom sides each enclose a hollow portion, which design strengthens the section modulus of the end cap, and also that of the conduit spacer to which it is attached, while adding little cost and weight. The tabs and slots of the spacers and end caps may also be considered as engaging rails and grooves.  FIGS. 2-4  are front views of the end caps. The open side of end caps  40   a ,  40   b  in the front view includes two arcs  42  for interfacing with a conduit. As may be seen slightly in  FIG. 2  and more clearly in  FIG. 8 , a rear view of the end caps and spacers  10 , the open side of end caps  40   a ,  40   b  is generally a semicircle rather than arcs. The additional material helps the end caps more firmly support the conduits when the duct bank is assembled. 
     The end caps may be described in other terms. For example, the end caps may be described as having a top surface, a bottom surface opposite the top surface, and an outer surface connecting the top and bottom surfaces. The outer surface would be the straight surface, the side surface opposite the tabs or slots. The open area in a general shape of a semicircle or arcs could be described as an inner surface. As is apparent from  FIGS. 2 and 8 , the inner surface does not contact the outer surface, since the top and bottom surfaces, as well as the tabs or slots, are situated between the inner and outer surfaces. 
     In addition, the end caps are not limited to the embodiments shown. For example, an end cap may take on a general shape of a hollow square or rectangle with an interior bore or surface in a generally circular shape. This embodiment also has at least one tab or at least one slot on one side of the square or rectangle. In this embodiment, the sides are the outer surfaces connecting the top and bottom surfaces, and the inner bore constitutes the inner surface. As is apparent from the embodiments depicted in the drawings, the end caps have two tabs or slots, a tab or slot proximate the top and bottom surfaces of the end cap. In other embodiments, there is only one tab or slot, proximate either the top or the bottom surface of the end cap. 
     Two or more spacers  10  may be stacked vertically, using the tabs  19  at the top of a lower spacer and the slots  15  at the bottom of a spacer stacked atop the first spacer. Such spacers may be stacked in the general shape of a plane, as shown in  FIG. 1 . The spacers may also be laid side-by-side, as shown in  FIG. 4 . In  FIG. 4 , first spacer embodiment  10  is joined to a second spacer embodiment  20 , using tabs  24  on the left side of spacer  10  and engagement slots on the right portion of spacer  20 . In this configuration, male end cap  40   b  is joined to the slots  26  of spacer  10  on the right while female end cap  40   a  fits onto tabs  24  of spacer  20  on the left side. Spacers  10 ,  20  and their end portions form a generally circular cavity suitable for accommodating a conduit of a smaller diameter, while their U-shaped bodies are typically designed for a larger diameter. Spacers  10  and  20  are horizontally interlocked at joint  47 , as are end caps  40   a ,  40   b , at other joints or intersections  49 . 
       FIG. 3  depicts spacer  20  in greater detail. Spacer  20  is designed to accommodate two conduits in adjacent U-shaped bodies  17 . U-shaped bodies  17  form generally about 270 degrees of a circle, molded so that the end portions or arms near tabs  19  and transitions  18 , are biased inwardly to create a snap fit. The base  12  of spacer  20  includes three flat portions  13  and two arcuate portions  14 . Base  12  also includes bosses  16  with internal slots  15 , not visible in this view. In one embodiment, the slots  15  are open on the front and rear. In other embodiments, the slots may be blind, that is, with only one end open to accommodate the engaging tab provided on the end of the U-shaped body for vertical stacking. Each U-shaped body  17  includes adjacent support structures  38  supported by a vertical rib  28  and additional ribs as shown. The U-shaped bodies are supported on the outer sides by buttresses  34  and on their inner sides by support structure  56 , which includes ribs as shown, and forming an additional circular conduit support  52 . Conduit support  52  is also supported by additional support structure  54  grounded to base  12 . 
     The spacers herein described may be molded from any of a number of plastic materials, such as HDPE, LDPE, PP, HIPS, ABS, and so forth, by injection molding. They may also be thermoformed, compression molded, or made by any other desired method. The conduits which are typically accommodated may be nominally 150 mm (about 6 inches) diameter, or other desired diameter, e.g., 100 mm (about 4 inches) or 200 mm (about 8 inches). The spacers may be designed and manufactured to accommodate other desired sizes. The smaller conduits are typically a nominal 75 mm (about 3 inches), but may be 50 mm (about 2 inches), or other desired size, such as 25 mm (about 1 inch) diameter. The spacers may be made to accommodate other desired sizes. 
     An important design criterion in duct banks is the spacing between adjacent conduits, whether spaced in a single spacer or spaced within an assembly of two or more spacers. Spacing is typically necessary to minimize any undesirable heat effects or electrical interference caused by proximity. Spacing may be specified between adjacent large conduits, between adjacent smaller conduits, or between large and small conduits. For example, vertical or horizontal spacing, or both, of 70 mm (about 3 inches) may be specified between large conduits. Other desired spacing may be specified and achieved by using the appropriate support structures, lengths and heights of the ribs, and so forth. It is also desirable for the bottom portion of the spacers to have sufficient area to support the duct bank. The width (front to back) of the spacers may be about 64 mm wide, for example. Other widths may be used as desired for appropriate support. In one embodiment for 6-inch (150 mm) conduit, the spacers are designed for a minimum of 70 mm, 75 mm or 3 inches of spacing, both vertically and horizontally, between conduits located in the U-shaped bodies. 
     An important feature of the conduit spacers described herein is that they may be joined or stacked vertically, as well as horizontally.  FIGS. 5 ,  5 A,  6 ,  6 A,  7  and  7 A disclose additional details of conduit spacer  10 . In the front view depicted in  FIG. 5 , three conduit spacers  10   a ,  10   b  and  10   c  are stacked and vertically interlocked atop each other along axis Y, each of the conduit spacers joined horizontally along axis X to end caps  40   a ,  40   b . Each conduit spacer accommodates a single conduit  6 . As noted previously, each conduit spacer includes a central vertical rib  28  and additional ribs  32 , which are at a slight angle from vertical. The angle may be from about 5 degrees to about 30 degrees. Other angles may be used, including a vertical orientation. 
       FIG. 5A  depicts a closer view of the conduit  6  and the left portion of the U-shaped body  17 . The U-shaped body  17  ends in a tab  19  connected by a transition portion  18 . As seen in  FIG. 5A , this embodiment of the transition portion  18  includes a straight portion between curved portions. This straight portion is believed to help lock the tab into place when two spacers are interlocked. In other embodiments, a gradual curve may be used instead. 
       FIGS. 6 ,  6 A,  7  and  7 A depict yet closer views of the tabs and slots of spacer  10 . In one embodiment, the tabs and slots are tapered, with a narrow portion of the slots ending blind, i.e., there is a blind slot, with the closed end on the front of the spacer. The tab is designed so that its narrow portion is inserted into the wide or open portion of the slot. Thus, in  FIGS. 6 and 6A , spacer  10  includes tab  19  with wide portion  19   a  and narrow tapered portion  19   b . The narrow portion  19   b  will be inserted into the slot. Narrow portion  19   b  will face the front of the spacer and wide portion  19   a  will face the rear of the spacer. The taper of the tabs in one embodiment is from about 0.5° to about 2° per side. In another embodiment, the taper is from about 1″ to about 2° per side. 
       FIGS. 7 and 7A  detail the placement and geometry of the slots. Slot  15  is molded into boss  16 , the slot opening into flat portion  13  of the base  12  of the spacer. In other embodiments, the slot may not open onto the bottom of the spacer and may form a completely blind slot. Slot  15  includes a wide, open portion  15   a  facing the rear of the spacer, with narrow portion  15   b  ending in a blind or closed end on the front face of the spacer. In this disclosure, a blind slot includes a slot with one portion open to the bottom, as seen in  FIGS. 7 and 7A , and also includes a completely blind slot with only a single opening, as in portion  15   a . In this embodiment, base arcuate portion  14  is adjacent, that is, touches, flat portion  13 , at least at the outer tip  13   a  of the flat portion. Accordingly, base  12  includes flats  13  that are adjacent and contiguous to the arcuate portion or portions of the spacer. In addition, the slots open to a bottom surface of the flat portions  13  of the spacer. The slots are oriented in one embodiment at an upward angle of 9 degrees from horizontal. Other embodiments have the slots oriented at an angle from about 0 degrees to about 45 degrees from horizontal. In yet another embodiment, the bosses and slots may be raised higher and the slots actually tilted downward at an angle. The taper of the slots in one embodiment is about 2° per side; in another embodiment, the taper is from about 0.5° to about 2° per side. 
     Base  12  includes a continuous run of material from the left side to the right side of the spacer, as seen in  FIG. 7 . The arcuate portion or portions  14  run directly to the feet or flat portions  13 , that is, the arcuate portions are contiguous with the feet and connect directly with the feet. The arcuate portions also directly support the U-shaped body for a large conduit through rib  28 . Thus, the design of spacer  10  is very strong, since the supports from the U-shaped body run directly through straight ribs  28 ,  32  to the arcuate section  14  or bosses  16  of base  12 . 
       FIGS. 8 ,  8 A and  8 B depict rear perspective views of stacked spacers with close-ups of the tapered tab-and-slot connections. In  FIG. 8 , three spacers  10   a ,  10   b  and  10   c  are stacked one atop another and are vertically interlocked with their tabs and slots. Each spacer houses a 150 mm conduit  6  and each spacer also is mated to a female end cap  40   a  on one side and to a male end cap  40   b  on the opposite side.  FIG. 8A  depicts an arm of a U-shaped body  17  from lower spacer  10   b  connecting to a slot  15  of upper spacer  10   c . The arm includes transition portion  18  and end tab  19 . Note that the outer face  19   a  of tab  19  is wide, while the tab tapers to a narrow, inner face  19   b , which is being inserted into the slot  15 . Slot  15  is a cavity in boss  16 . As noted above, slot  15  is also tapered as shown in  FIG. 7A . Since slot  15  is blind, the open, wider end is the portion visible in  FIG. 8A , and is the end into which the tab  19  is being inserted. Note that both the tab and the slot taper, that is they narrow, in the direction of the width of the spacer, axis Z, i.e., the narrowest of the three dimensions of the conduit spacer. Note also that slot  15  opens onto flat portion or foot  13 . 
     In  FIG. 8B , tab  19  has been inserted into slot  15  of boss  16 . Note that the insertion length of tab  19  is less than the insertion length of slot  15 , allowing tab  19  to be inserted completely into the slot. In one embodiment, the slot length is about twice the length of the tab, both in the direction of axis Z. This allows for easier assembly, since a little play is allowed in making the connections. 
       FIGS. 9 ,  9 A- 9 D and  10 A- 10 D disclose additional embodiments and views of the spacers and the slots and tabs.  FIG. 9  is a rear elevation of a stack of conduit spacers, similar to the embodiment of  FIG. 8 , with the conduit spacers in a stacked configuration. Spacer  10   a  rests on the ground and is connected to end caps  40   a ,  40   b , as are spacers  10   b ,  10   c . Spacer  10   b  is atop spacer  10   a  and is connected to spacer  10   a  with the tab-and-slot arrangement discussed above. Spacer  10   c  is atop spacer  10   b  and is also connected with tabs and slots. Each of the spacers contains a conduit  6 . 
     As shown in  FIG. 9A , top spacer  10   c  includes a boss  16  with a slot  15  while middle spacer  10   b  includes tab  19 .  FIG. 9B  depicts tab  19  about to be inserted into the slot in the general direction of axis Z. Tab  19  is tapered along axis Z in the direction of the width of the spacer, with a wider end  19   a  and narrow end  19   b , and is shown in cross section in the perpendicular orientation of  FIG. 9B . Slot  15  also has a wide end  15   a  and a narrow or blind end  15   b .  FIGS. 9C-9D  depict the tab  19  inserted into the slot. Note that the length of the slot  15 , along axis Z, is considerably longer, about twice as long, as a length of the tab  19 . 
     Another embodiment of slots and tabs is depicted in  FIGS. 10A-10D , which the slots have a separate and distinct lead-in section. As shown in  FIG. 10A , middle spacer  10   b  has a boss  56  with an internal slot  55 , while bottom spacer  10   a  has a tab  19 . Slot  55  includes a lead-in portion  57 , an intersection  55   a  and a blind end  55   b . The lead-in  57  is tapered at a first wide angle, allowing for easier engagement with the tab  19 . The slot angle changes at the intersection  55   a  to a narrower angle, and then continues to the blind end  55   b . For example, the wider first angle may be about 8 degrees per side, and the angle following the intersection  55   a  may be about 2 degrees per side. Other embodiments may use other angles. As noted above, the tab  19  has a length less than a length of the slot, allowing for complete insertion of the tab  19  into slot  55 . 
     All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. Skilled artisans will use such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.