Abstract:
A stackable riser having a substantially smooth outer surface has a first open end defined by an edge and a second open end defined by a pair of adjacent channels, so that the edge defining the first open end of a first riser can mate with one of the channels defining the second open end of a second riser. A detachable anchor tab extends radially from the outer surface about the circumference of the riser. A plurality of risers can be stacked one on top of another, with, for example, the bottommost riser embedded in concrete and the risers above it embedded in soil. Preferably, the anchor tab of the bottommost riser remains attached to the riser and the anchor tab of the risers above it is removed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention pertains to stackable risers. More particularly, the present invention pertains to a system and method of connecting a series of risers in a way that provides improved vertical support, minimizes the effect of frost heaving and other forces due to vertical ground movement, and resists rotational forces resulting from lateral ground movement. 
     2. Background of the Invention 
     Meters, splices, junction boxes, and other components of buried utility systems are often located inside hand-holes or manholes to enable easy access by utility workers from aboveground. Often, utility systems provide such access facilities at key points, such as a major bend in an underground cable/conduit run or location of water or gas meters and other equipment subject to frequent servicing or inspection. Such access facilities have been constructed using preformed or poured concrete side retaining walls. Concrete can be expensive, particularly where the application requires a non-standard size or length, in which case setting forms and pouring concrete adds time and expense. Also, over time, the concrete can crack due to forces caused, for example, by freezing and thawing or by heavy vehicles being driven over the top of the manhole. Tiled sidewalls and concrete block are examples of other labor intensive alternatives. 
     Injection molded, plastic, stackable risers made of high density polyethylene and other rigid, light weight polymeric material are known in the art and provide a less expensive, standardized alternative that lends itself to rapid on site customization. Risers can be manufactured in various heights and diameters and a series of identically sized risers can be stacked to achieve a desired depth. 
     Depending on the soil characteristics and overhead traffic, the vertical, horizontal, and rotational forces placed upon these risers can be considerable. A major shortcoming of plastic risers lies in their tendency to deform or break when subjected to such forces. The use of vertical and horizontal strengthening ribs to alleviate this tendency is common. When placed along the exterior of the sidewall, however, these reinforcing ribs themselves often are subjected to the same vertical and horizontal forces they are intended to protect against. 
     U.S. Pat. No. 5,852,901 for a “Stackable Riser for On-Site Waste and Drainage Systems,” issued to Meyers illustrates one prior art design of a plastic riser for forming a depth-adjustable, grade-level access for underground components. The Meyers riser forms a rigid structure intended to support heavy loads applied to the grade level access lid. Identical risers reinforced along portions of both the inner and outer walls are stacked one on top of the other utilizing a single tongue and groove connection. A horizontal rib extending outward along the circumference of the external surface of the side wall of each cylindrical riser and a plurality of vertical ribs, also on the external surface of the riser, individually anchor each riser in the ground. A plurality of risers can be stacked to form a vertical, air-tight, liquid-tight, and gas-tight riser and lid system. 
     The shifting of the ground surrounding the riser stack disclosed in the Meyers patent can twist and move the stacked risers, knocking them out of alignment. Eventually, the shifting can lead to rupture of the stacked risers&#39; sidewall. The presence of external horizontal and vertical reinforcing ribs extending along the wall of each riser, while strengthening the riser sidewalls, also exacerbates this problem because shifting soil applies force against each exposed rib. The configuration of the tongue and groove arrangement of the risers disclosed in the Meyers patent also precludes the placement of supporting ribs along the full vertical length of the interior riser wall, which lessens the sidewall&#39;s resistance to forces exerted by the shifting of the soil abutting the sidewalls and external ribs. 
     SUMMARY OF INVENTION 
     The stackable riser of the present invention addresses these shortcomings. In the preferred embodiment, the stackable riser of the present invention has a hollow, cylindrical configuration, although configurations other than cylindrical may be used. The sidewall of the riser includes a channel end and a tapered end. In the preferred embodiment, the riser has a nearly smooth exterior surface from which projects outwardly a detachable anchor tab that may run along substantially the full circumference of the riser. The channel end of the riser sidewall includes two adjoining channels which are defined by interior, middle, and exterior walls that project concentrically with, or (in the case of risers having, for example, a square or rectangular cross-section) parallel to, the sidewall. The opposite, or tapered, end of the riser sidewall terminates in a portion tapered to a narrower thickness at the end. A plurality of vertical reinforcing ribs are spaced around the interior surface of the cylindrical sidewall of the riser. Because in the preferred embodiment the ribs extend from near the channel end to the distal end of the tapered end of the riser sidewall, they strengthen the sidewall in the area of the joint between each pair of stacked risers. In the preferred embodiment, the interior surface of the sidewall also includes at least one boss extending vertically from near the channel end to the distal end of the tapered end of the riser. Each boss is adapted to receive a screw, or other fastener, for securing another riser stacked on top of the first riser, or a cover at ground level. 
     The tapered end of the riser sidewall is configured to mate with the two concentric channels of either another riser or a cover. The radially outer channel is shallower than the inner channel in the preferred embodiment and accepts the tapered end of the sidewall of another riser on which it is placed. The radially inner channel is wider than the outer channel, and accepts the interior vertical support ribs and bosses of a riser on which it rests. An O-ring placed in the outer channel can be used to effect a water-tight and gas-tight seal between two stacked riser sections (or between a riser and a cover). Sealant can be applied to the area where the tapered end of a first riser contacts the outer channel of another riser (or a cover) stacked on top of the first riser to further ensure a water-tight, gas-tight seal between adjacent risers (or between a riser and a cover) beyond that provided by the dual channel design of the present invention. 
     In the preferred embodiment, a detachable anchor tab on the exterior surface of the riser sidewall serves to anchor the lower-most riser in concrete, for example, a cast-in-place concrete distribution box. The concrete is poured around the riser and its anchor tab, thereby anchoring the bottom riser after the concrete hardens. Another identical riser may be placed on top of the bottom riser, with the tapered end of the bottom riser mating with the channel end of the riser placed on top of the bottom riser. The anchor tab on each of the risers stacked above the bottom riser (i.e., above the riser anchored in the concrete box) in a given stack can be detached by tearing it away from the exterior of the sidewall. In the preferred embodiment, the anchor tab includes a handle for this purpose. Tearing away the anchor tabs on the risers that are not anchored in concrete gives the stack of risers a nearly smooth exterior surface, thereby minimizing the forces exerted on the stack of risers by movement of the soil in contact with the riser stack. 
     In alternative embodiments of the present invention, the risers may have a square, rectangular, elliptical or other cross-sectional configuration. 
     It is an object of the present invention to provide an improved connection configuration that resists rotational forces exerted on one or more risers in an interconnected system. 
     It is another object of the present invention to provide improved reinforcement of the sidewalls of risers stacked one on top of the other. 
     It is still another object of the present invention to provide a detachable anchor on the exterior surface of a riser, the anchor being used when the riser is to be anchored in concrete, and removed when the riser is to be in contact with soil. 
     It is a further object of the present invention to provide a riser adapted for being anchored in concrete, while at the same time minimizing the susceptibility of a stack of risers to forces caused by the ground next to the stack shifting. 
     Other features, objects and advantages of the invention will become apparent from the following description and drawings in which the details of the invention are fully and completely disclosed as part of this specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view of a cylindrical stackable riser of the present invention; 
     FIG. 2 is a cross-section view of the stackable riser of the present invention taken along line  2 — 2  in FIG. 1; 
     FIG. 2A is a cross-section view of a cover for overlying a stackable riser of the present invention; 
     FIG. 3 is a side view of a cylindrical stackable riser of the present invention; and 
     FIG. 4 is perspective view of a cylindrical stackable riser of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1,  2 ,  3  and  4 , in the preferred embodiment of the present invention a stackable riser  10  includes sidewall  12  having a plurality of vertical bosses  24  and a plurality of vertical reinforcing ribs  26 . Attached to the substantially smooth exterior surface of sidewall  12  is detachable anchor tab  14  (discussed below). Sidewall  12  has a tapered end  37  and a channel end  27 . (In an alternative embodiment, end  37  could be straight rather than tapered.) In the preferred embodiment, tapered end  37  includes on the external surface of sidewall  12  a horizontal edge surface  38  (i.e., edge surface  38  is substantially perpendicular to the axis of the riser and the external face of sidewall  12 ). With reference to FIG. 4, edge surface  38  extends around the circumference of sidewall  12 . End  37  includes a tapered portion  30  extending from horizontal edge surface  38  to the distal end of tapered end  37  of sidewall  12  and riser  10 . End  37  of riser  10  includes the ends  40   b  and  40   r  of vertical bosses  24  and ribs  26 , respectively, the ends  40   b ,  40   r  being flush with the horizontal edge  40  on the end of tapered portion  30  of sidewall  12 . Tapered end  37  thereby forms a unique male connector. The opposite end of riser  10  forms a corresponding female connector, referred to herein as channel end  27 , as described below. 
     Referring to FIGS. 2,  3  and  4 , the channel end  27  of riser  10  comprises a unique dual channel arrangement in which outer wall  18 , middle wall  20 , and inner wall  22  extend downward from, and are generally parallel to, sidewall  12 . Horizontal ledge  28  on the interior surface of sidewall  12  (see FIGS. 1,  2  and  4 ) is generally perpendicular to sidewall  12 . As shown in FIGS. 2 and 4, bosses  24  and ribs  26  extend vertically from ledge  28  to the distal end  40  of tapered end  37 . Bosses  24  are attached to or formed on the interior surface of sidewall  12  by an offsetting portion  24   a  (see FIG. 4) that extends from the inside surface of sidewall  12  to the boss  24 . The relatively narrow width of slots  16  in middle wall  20 , as shown in FIGS. 3 and 4, substantially limits any rotation of riser  10  with respect to another riser  10  stacked above or below the first riser because the offsetting portions  24   a  of bosses  24  and the ribs  26  pass through and are restricted against angular lateral movement by the sides of slots  16 . The top surfaces  40   b  of offsetting portions  24   a  and bosses  24  and top surfaces  40   r  of ribs  26  are flush with the top surface  40  of tapered end  37 . Referring to FIG. 2, when the tapered end  37  of one riser  10  and channel end  27  of another riser  10  are mated, top edge  40  of tapered portion  30  is positioned within outer channel  19 , which is the channel or space between inner surface  32  of outer wall  18  and outer surface  46  of middle wall  20 . Bottom edge  36  of outer wall  18  thus rests upon edge  38  on the exterior surface of sidewall  12 . 
     As shown in FIGS. 2-4, channel end  27  of the present invention includes middle wall  20  having slots  16  at regular intervals. The slots  16  are spaced in middle wall  20  of a first riser  10  such that they align with offsetting portions  24   a  of bosses  24  and with ribs  26  of an end  37  of a second riser  10  when the first riser is placed on top of the second riser. Bosses  24  and ribs  26  of the second riser  10  thereby extend into inner channel  23  of the first riser  10 . With reference to FIGS. 2 and 3, each slot  16  extends from end  20   a  of wall  20  to top  16   a . The top  16   a  of each slot  16  is flush with the end  42   a  of a vertical projection  42  in inner channel  23 . Each projection  42  (shown partially by the phantom lines in FIG. 3) projects into outer channel  23  a height indicated by line  48  (see FIG.  2 ). Offsetting portions  24   a  of bosses  24  and supporting ribs  26  of a first riser are adapted to slide into slots  16  in a second riser when the second riser is placed on top of the first riser. In a preferred embodiment, slots  16  and corresponding projections  42  are spaced midway between bosses  24  and ribs  26 , which increases the structural integrity of the riser  10 . In one embodiment, a riser is rotated 15° with respect to a riser above or below it in a stack. Additional risers  10  can be stacked above or below the first and second risers, as desired. 
     When one riser is placed on top of another, top edge  40  of the riser on the bottom projects into outer channel  19 . In the preferred embodiment, an O-ring (not shown) is positioned at the bottom  19   a  of outer channel  19  such that when the first riser is placed on top of a second riser top edge  40  of tapered end  37  abuts against the O-ring (not shown) to provide a substantially water-tight and gas-tight seal. The height  48  of projecting members  42  is such that the top edges  42   a  of projecting members  42  abut against edges  40   b  and  40   r  of bosses  24  and ribs  26 , respectively, of the second riser. Accordingly, sidewalls  12  are reinforced along the full height of sidewall  12  by the combined height of projections  42  and either bosses  24  or ribs  26 . Outer wall  18  and middle wall  22  prevent horizontal movement of two stacked risers  10  with respect to each other. 
     In the preferred embodiment, vertical support bosses  24  are cylindrical in shape and, as noted above, are attached to the interior surface of sidewall  12  by connecting member or offsetting portion  24   a , which preferably runs along the full vertical height of each boss  26 . As shown in FIG. 3, when two risers  10  are placed one on top of the other, slot  16  can accept either, referring now to FIG. 2, top edge  40   r  of a rib  26  or top edge  40   b  of offsetting portion  24   a  of a boss  24 . 
     The vertical bosses  24  each contain on their end  40   b  a hollow bore adapted to accept a screw, or other suitable fastener. Similarly, each projection  42  in a first riser  10  that is aligned with a boss  24  of a second riser  10  may contain such a hollow bore (not shown) so that a screw or other suitable fastener (not shown) can be inserted through projection  42  in the first riser  10  into the top end of a boss  24  below it in a second riser  10  to thereby fasten the two risers together. In that case, ledge  28  contains an opening  52  over the projections  42  having the hollow bores (not shown) so that a screw or other fastener may be inserted through projection  42  and into the top end  40   b  of boss  24  below it when two risers  10  are stacked. A lid  50  (see FIG. 2A) can cover the uppermost riser  10  in a stack of risers  10 . The lid  50  may have the same configuration as the channel end of risers  10  and may include projections  42  having hollow bores for accepting screws or other fasteners as described above for fastening two risers  10  together. 
     Alternatively, the tapered ends  37  could be on the bottom and the channel ends could be on the top in a stack of risers  10  of the present invention. In this configuration, the lid  50  has an end with the same configuration as tapered end  37  of risers  10 . 
     Referring to FIGS. 1,  2  and  3 , detachable anchor tab  14  runs along the outside surface of the sidewall  12 . The bottom-most riser  10  within a vertical stack may be cast in concrete (e.g., a concrete distribution box not shown), in which case anchor tab  14  serves to anchor the bottom-most riser  10  within the concrete. In the preferred embodiment, pull handle  15  is attached near ends  13   a ,  13   b  of anchor tab  14 . Anchor tab  14  is severed or has a weakened cross-section at ends  13   a ,  13   b  such that pulling on handle  15  in a radial direction separates ends  13   a  and  13   b . Preferably, anchor tab  14  is attached to the outside of sidewall  12  by a weakened region  14   a , such that continuing to pull handle  15  away from the sidewall  12  causes anchor tab  14  to tear away form the outside surface of riser  10  in region  14   a . Anchor tab  14  is preferably completely removed from riser  10  when riser  10  is not intended to be cast in concrete. Detaching anchor tab  14  from each of the risers placed above the bottom-most riser (i.e., all of the risers except the bottom one that is cast in concrete) enhances the stability of the entire stack by providing a substantially smooth external surface that is less susceptible to forces caused by ground heaving and shifting than if the external surface contained the anchor tabs  14  (or any other projecting elements, such as support ribs). In this way, the alignment and integrity of the overall riser stack is maintained in areas subject to soil movement caused by freezing and thawing or heavy traffic over the top of the riser. 
     Whereas the present invention is described herein with respect to specific embodiments thereof, it will be understood that various changes and modifications may be made by one skilled in the art without departing from the scope of the invention, and it is intended that the invention encompass such changes and modifications as fall within the scope of the appended claims.