[0001]     This application is a divisional-continuation of patent application Ser. No. 10/402,414 of Kruger et al., filed Mar. 28, 2004, which was a continuation in part of application Ser. No. 09/849,768, filed May 24, 2001. This application claims benefit of provisional applications Ser. No. 60/202,255, filed May 5, 2000 and No. 60/368,764 filed Mar. 29, 2002. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention relates to molded non-metal chambers for subsurface receipt and dispersal of waters, in particular to molded plastic chambers for receiving stormwater.  
       BACKGROUND  
       [0003]     In use, a storm water chamber is buried beneath the surface of the earth, to collect storm water, such as runoff from parking lots and the like. In a typical stormwater chamber installation, a multiplicity of chambers is laid into cavities in the earth as large array, and then covered over with gravel, stone or soil. See U.S. Pat. Nos. 5,156,488, 5,511,903 and 5,890,838 for examples of chambers. Often the chambers are placed on and buried in gravel; and overlaid with more gravel or soil or a paved surface for motor vehicle traffic or parking. Thus, it is important that they be structurally sound.  
       SUMMARY  
       [0004]     An object of the invention is to provide stormwater chambers and related components, including end plates, which are strong, economic to produce, which nest well for shipping, which connect together well, and which are adapted for receiving internal flow control baffles.  
         [0005]     In accord with the invention, an arch shape cross section chamber for receiving and dispersing stormwater when buried beneath the surface of the earth is corrugated and has a cross section geometry which preferably is a continuous curve.  
         [0006]     In further accord with the invention, the chamber is used in combination with a domed end plate, or end cap, which fits onto the end of the chamber to prevent gravel and soil from entering, preferably by engaging a corrugation at the chamber end. The preferred end plate has a dished portion which projects outwardly (i.e., convexly) from the end of the chamber, and it has cross hatch ribbing on the interior side. A hole may be cut in the end plate, so an input pipe can deliver water to the chamber.  
         [0007]     In further accord with the invention, the end plate and chamber are shaped so the flange outer edge of the end plate fits within the corrugations in the central part of the chamber, which corrugations are larger than those at one end. When so positioned, and when the dome has a cut out at an elevation substantially above the elevation of the base, water flow from one part of the chamber, or from one part of a series of interconnected chambers to another part, is inhibited.  
         [0008]     Preferably, the curve of the chamber is a truncated semi-ellipse, that is, less than half an ellipse, wherein the major axis of the ellipse lies along the vertical axis of the chamber. Thus, the vertical height of the chamber interior is less than half of the length of the major axis of the semi-ellipse of which the chamber geometry is a portion.  
         [0009]     In further accord with the invention, a storm water chamber comprises a combination of standard corrugations along most of the length, in combination with smaller one-end corrugations, to enable joining of chambers in overlap fashion, as a string; corrugations which have elliptically curved corrugation widths when viewed from the side of the chamber; and, sidewall base flanges which have turned up outer edges in combination with fins which connect said edges with the curved chamber sidewall.  
         [0010]     The foregoing and other objects, features and advantages of the invention will become more apparent from the following description of preferred embodiments and accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0011]      FIG. 1  is a partial isometric view of a molded plastic chamber.  
         [0012]      FIG. 2  is an end view of a chamber like that in  FIG. 1 , with a stepped end plate attached at the end.  
         [0013]      FIG. 3  is a side elevation view of a chamber with a stepped end plate attached to one end.  
         [0014]      FIG. 4  is a side elevation view of a chamber having a dome end plate at one end, where the convex surface dished out portion thereof faces outwardly.  
         [0015]      FIG. 5  is a fragmentary lengthwise cross section of the joint formed between two mated chambers.  
         [0016]      FIG. 6  is a fragmentary isometric view of the end of a chamber like that in  FIG. 1 , to illustrate details at the base of the chamber sidewall.  
         [0017]      FIG. 7  is an isometric view of an end plate having a dished portion.  
         [0018]      FIG. 8  is an isometric view of the interior of the end plate of  FIG. 7 .  
         [0019]      FIG. 9  is a side elevation view of a portion of a chamber, to illustrate corrugation contour in the vertical plane.  
     
    
     DESCRIPTION  
       [0020]     The present invention is described in pending U.S. patent Ser. No. 09/849,768 and No. 10/402,414, both of Kruger et al.,. The disclosure and drawings thereof are hereby incorporated by reference. The present invention is also described in two provisional patent applications, namely Ser. No. 60/202,255, filed May 5, 2000, and Ser. No. 60/368,764 filed Mar. 29, 2003, the disclosures of which are also hereby incorporated by reference.  
         [0021]     In the incorporated references, the invention is variously referred to as a storm management system and, in part, as a corrugated stormwater chamber. A typical chamber may be 45-50 inch wide at the base by 30 inch high at the peak interior and 91 inch long. It is preferably made of injection molded high density polypropylene, polyethylene or comparable material. Preferably it is made by injection molding, for precision, although other known methods of fabrication may alternatively be used.  
         [0022]      FIG. 1  shows a molded plastic chamber  20  having a continuous an arch shape cross section and corrugations  24  running along the arch shape from opposing side base flanges  36 . The chamber has a longitudinal axis L and a vertical axis A. See also  FIG. 2 . Preferably, the chamber has a continuous curve cross section geometry, for strength. More particularly, the chamber has a cross section geometry which is a truncated semi-ellipse, as illustrated by  FIG. 2  (which shows an end plate  21 A in place, which is discussed below). The geometry is less than half an ellipse  100 , the major axis A of which lies along the vertical axis of the chamber. Thus, the vertical height is less than half of the length of the major axis of the semi-ellipse. As shown in  FIG. 2 , the chamber has an inner height H and an inner width W. Preferably, the chamber has a width to height ratio (W/H) between about 0.5 to 1 and 2 to 1, more preferably between 1 to 1 and 2 to 1. Preferably, the height H is between about 44 and 48 percent of the length of the major axis of the ellipse of which the truncated semi-ellipse is a portion.  
         [0023]     The bulk of the body of the chamber has corrugations  29  of a standard dimension, including first end corrugation  28 , except for at least a smaller second end corrugation  26 . See  FIG. 4 . The difference in dimension between corrugation  26  and the “standard” corrugation is roughly equal to or greater than the wall thickness of the chamber at the corrugations, which thickness will be typically in the range 0.150-0.188 inch for an injection molded chamber.  
         [0024]     Thus, as shown in the partial vertical center-plane cross section of  FIG. 5 , the first end of a first chamber  20  can be laid on top of the second end of a second chamber  20 P, so the chambers may thereby be joined together in the form a string of chambers. If a shorter chamber length is desired, as when a factory-made chamber is too long for the application, the chamber may be cut, for instance, at the chamber midpoint in a valley. Thus the corrugation which is at the newly cut end of the chamber can be engaged with the smaller corrugation  26  at the second end of another chamber, overlapping it, to form a joint.  
         [0025]     The opposing side base flanges  36  have turned up outer edges  102 , called support members, for providing strength in the longitudinal direction. See  FIG. 6 . The base flanges  36  have cutout portions  50  at one end, where the large corrugation  28  is. See  FIG. 1 . Thus, when chambers are overlapped to form a string, the flanges  36  of the small end fit within the cutouts, and the chambers better fit together, than would be the case without the cutouts.  
         [0026]     An end plate  21 ,  21 A, preferably the kind of end plate which is also called an end dome here, is used to close off the open end of a chamber, as shown in the side elevation views of  FIG. 3  and  FIG. 4 . The two embodiments of end domes  21 ,  21 A have corresponding parts denoted by numerals with suffixes. The end dome  21  has a dished or convex shape portion  22  (as viewed from the exterior of the chamber, when installed) and an arch shape flange  30  running around the dished portion. Compared to the essentially flat end plates of the prior art, the end dome has improved resistance to the load of encompassing compactable media such as crushed stone or soil which impinges on the dome when the chamber is buried and in use. The dished shape also provides more volume to the interior of a closed-off chamber than does a flat end.  
         [0027]      FIGS. 7 and 8  show end dome  21 . The interior of the dome has cross hatch ribbing  32 , to provide further strength to the dished portion. The arch shape flange  30  of the end dome has an outer shape which is less than or equal to the outside dimension of a smaller corrugation  26  of the chamber. Thus, the flange  30  slips within corrugation  28  at the first end of the chamber  24 , just as does the smaller corrugation  26  of another chamber. Preferably, the fit of flange  30  at end corrugation  28  is intentionally looser than the fit of the smaller corrugation  26 , to the extent that the flange will also fit within the smaller opposing end corrugation  26  of a chamber. Thus only one-design end dome is needed for closing both ends of chamber  20 , with its differing dimension end corrugations. In the generality of the invention, the end dome described here can be used on other kinds of chambers, including leaching chambers. The flange  30  of a preferred end dome  21  can also fit within any of the other corrugations  29  of the chamber  20 , along the chamber length. Thus, if the chamber  20  is cut at any point along its length, to form a shortened length chamber, the end dome can be used as a closure at the cut end.  
         [0028]     When soil pushes on the dome end plate, there is a lateral outward force, as the dished portion tries to flatten. So, the loose fit referred to above is not so loose as to prevent the dome flange or periphery from engaging the inside of a chamber corrugation and pushing outwardly on it. Since the chamber is backed by soil or stone lying along the length of the chamber, the chamber in vicinity of said corrugation resists the outward force. Thus, the dome endplate in the invention provides substantially greater strength and stiffness than does a flat end plate.  
         [0029]     The shape of the dished portion  22  of an end dome may vary. Dished portion  22  may have different contours which include those which may be characterized as semi-rounded, bowed, semi-spherical (and, when considering both the exterior and interior of the end dome) plano-convex, convexo-concave and convexo-convexo.  FIGS. 3, 4 ,  7  and  8  show that a preferred dished portion  22  of end plate  21  is a truncated, preferably curved, structure; and, the bottom of the dished portion is free of any flange and bulges outwardly from vertical plane of the flange and the associated chamber end. The base ends of the arch shape flange  52 ,  54  of the end plate  21  are at the same horizontal elevation of the base flanges  36  of a chamber when the dome closes off the end of a chamber. See  FIG. 7  and  FIG. 3-4 .  
         [0030]      FIGS. 2 and 3  show another end plate embodiment, namely end dome  21 A. The dished portion  22 A of the end dome comprises a series of generally arch shape steps  23 ,  25 ,  27 , which will support a pipe passing through the end dome. Preferably, the steps have a substantially concave or scalloped upper portion. See portion  31  of step  27  in  FIG. 2 .  
         [0031]     An end dome preferably has scoring which define places for circular cutouts or holes for a pipe which can carry water to or from the interior of chamber Cutout scoring  24  is shown for end dome  22  in  FIG. 7 .  
         [0032]     The end dome may engage the end of a chamber in alternative ways, compared to the flange being captured within a corrugation as described above. For example, the end plate may engage a chamber end by means of protrusions which engage divots or openings in the chamber, or by one or more snap connectors that engage a lip at the open end of the chamber. A dome endplate  21  which has a flange which fits into the corrugations of the chamber  20 , as described above, can be positioned within a corrugation at any point along the length of the chamber, to provide a baffle or act as a weir. In one such use, the dome may have a cutout or through-hole at an elevation. Alternatively, with the kind of loose fit mentioned above, there can be flow through the gap between the end dome and the chamber corrugation, so the end dome functions like a weir. If it is desired to prevent such flow, appropriate sealant or gasketing can be employed. Using a dome-as-weir creates subchambers within the length of a chamber. More than one dome may be positioned along the length of a chamber to create a multiplicity of subchambers. The dome-as-weir is used to make the subchamber function as a reservoir and settlement basin. Thus, water flowing along the length of the chamber will stagnate in velocity and desirable settling of entrained debris will be realized. Thus, by strategic placement of dome-weirs along the length of the chamber near the inlet end of a string of chambers, a preferential region for settlement of heavier than water debris is created. Cleaning is made easier. While the dome shaped end plate is preferred when a weir is desired, in the generality of this aspect of the invention, flat end plates may be used as weirs.  
         [0033]     The chamber has another feature which is characterized by an approximate or exact elliptical curve. This is appreciated when the chamber length is viewed from the side in elevation, as in  FIG. 9 . The edge b of each peak corrugation  29 , shown in somewhat exaggerated fashion in  FIG. 9 , is contoured as a segment of an imaginary second ellipse  40 . The shape, and location in space relative to the chamber, of the second ellipse is selected so the corrugation tapers inwardly in side view, running toward the top  42  of the peak corrugation, as shown in the Figure. When chambers are stacked, the elliptical curve shape enables better nesting of the chambers than does a corrugation which has either no taper, or which has straightline or planar taper, both referenced to the vertical cross sectional plane. The straightline taper, used in some prior art devices, either will not provide sufficient nestability, or will result in a corrugation width at the top becoming near zero, which is not good for strength.  
         [0034]     In another aspect of the invention, the chamber has vertical standoffs in the form of fins  44 , also called connecting elements, which are spaced apart along the opposing side base flanges  36 . Fins  44  connect outer edges  102  with the sides of the peak corrugations of the nearby chamber sidewall, to provide support to the flanges in the direction normal to the length of the chamber. See  FIGS. 1, 3 ,  4  and  6 . The height of the fins is chosen to prevent the chambers from jamming one onto the other.  
         [0035]     The inventions may be applied to chambers that have configurations other than the exemplary chambers; and, they may be applied to chambers used for other purposes than receiving and dispersing stormwater. For instance, the inventions may be applied to wastewater leaching chambers and to other arch like devices adapted for dispersing or gathering waters into or from soil and granular media.  
         [0036]     Although this invention has been shown and described with respect to a preferred embodiment, it will be understood by those skilled in this art that various changes in form and detail thereof may be made without departing from the spirit and scope of the claimed invention.
An end plate for closing off the end of an arch shape cross section corrugated stormwater chamber, which receives water for dispersal beneath the surface of the earth, has a dished portion which projects outwardly from the end of a chamber to which it is attached, preferably by means of a flange which engages the corrugations of the chamber. Ribs inside the end plate add strength.