Stackable riser resistant to soil movement

[0002] 1. Field of the Invention

[0003] 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.

[0004] 2. Background of the Invention

[0005] 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.

[0006] 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.

[0007] 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.

[0008] 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.

[0009] 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' 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's resistance to forces exerted by the shifting of the soil abutting the sidewalls and external ribs.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] In alternative embodiments of the present invention, the risers may have a square, rectangular, elliptical or other cross-sectional configuration.

[0014] 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.

[0015] It is another object of the present invention to provide improved reinforcement of the sidewalls of risers stacked one on top of the other.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] FIG. 1 is a top view of a cylindrical stackable riser of the present invention;

[0020] FIG. 2 is a cross-section view of the stackable riser of the present invention taken along line 2—2 in FIG. 1;

[0021] FIG. 2A is a cross-section view of a cover for overlying a stackable riser of the present invention;

[0022] FIG. 3 is a side view of a cylindrical stackable riser of the present invention; and

[0023] FIG. 4 is perspective view of a cylindrical stackable riser of the present invention.

[0024] 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 40band 40rof vertical bosses 24 and ribs 26, respectively, the ends 40b, 40rbeing 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.

[0025] 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 24a(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 24aof bosses 24 and the ribs 26 pass through and are restricted against angular lateral movement by the sides of slots 16. The top surfaces 40bof offsetting portions 24aand bosses 24 and top surfaces 40rof 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.

[0026] 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 24aof 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 20aof wall 20 to top 16a. The top 16aof each slot 16 is flush with the end 42aof 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 24aof 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.

[0027] 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 19aof 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 42aof projecting members 42 abut against edges 40band 40rof 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.

[0028] 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 24a, 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 40rof a rib 26 or top edge 40bof offsetting portion 24aof a boss 24.

[0029] The vertical bosses 24 each contain on their end 40ba 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 40bof 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.

[0030] 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.

[0031] 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 13a, 13bof anchor tab 14. Anchor tab 14 is severed or has a weakened cross-section at ends 13a, 13bsuch that pulling on handle 15 in a radial direction separates ends 13aand 13b. Preferably, anchor tab 14 is attached to the outside of sidewall 12 by a weakened region 14a, 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 14a. 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.

[0032] 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.