Manhole grade ring

Abstract

Several improved manhole grade rings and methods for providing improved manhole grade rings. In one embodiment, a plurality of concentric annular rings are connected by radial ribs. Certain radial ribs can be broken to provide a manhole grade ring of the desired diameter. In several other embodiments, concentric annular ribs and interconnecting radial ribs provide lightweight stackable manhole grade rings. In another embodiment, a manhole grade ring defines an annular cavity that can be filled to reinforce the manhole grade ring. Two embodiments provide improved forms for pouring manhole grade rings in place. One form provides a plurality of forms of different diameters that can be filled to any height, while another form provides adjustable height of the manhole grade ring.

1 ) An adjustable plastic manhole grade ring comprising:
 a plurality of concentric annular vertical ribs including a first pair of annular vertical ribs and a second pair of annular vertical ribs;   a first horizontal annular wall connecting the first pair of annular vertical ribs to one another; and   a plurality of radial ribs connecting the first pair of annular vertical ribs to the second pair of annular vertical ribs.   
   
   
       2 ) The adjustable plastic manhole grade ring of  claim 1  further including a second horizontal annular wall connecting the second pair of annular vertical ribs to one another. 
   
   
       3 ) The adjustable plastic manhole grade ring of  claim 1  further including first cylindrical ribs reinforcing the first horizontal wall. 
   
   
       4 ) A plastic manhole grade ring comprising:
 a plurality of concentric annular vertical ribs including a first annular vertical wall and a second annular vertical wall;   a first horizontal annular wall connecting the first annular vertical wall to the second annular vertical wall;   a seal secured to an upper surface of one of the annular vertical walls or the first horizontal annular wall; and   a plurality of radial ribs extending radially outward from the second annular vertical wall.   
   
   
       5 ) The adjustable plastic manhole grade ring of  claim 4  further including a third annular vertical wall connected to the plurality of radial ribs. 
   
   
       6 ) The adjustable plastic manhole grade ring of  claim 5  further including a second horizontal annular wall connecting the second annular vertical wall to the third annular vertical wall. 
   
   
       7 ) The adjustable manhole grade ring of  claim 5  wherein the first horizontal annular wall is a lower wall and the second horizontal annular wall is an upper wall. 
   
   
       8 ) The adjustable plastic manhole grade ring of  claim 4  further including openings through the second annular horizontal wall. 
   
   
       9 ) The adjustable manhole grade ring of  claim 8  wherein the openings also extend through the third annular vertical wall. 
   
   
       10 ) The adjustable plastic manhole grade ring of  claim 4  further including an annular channel for receiving the seal of a similar manhole grade ring stacked therebelow. 
   
   
       11 ) The adjustable plastic manhole grade ring of  claim 10  further including a lip protruding downward from the third annular vertical rib adjacent the channel. 
   
   
       12 ) A plastic manhole grade ring comprising:
 a first annular vertical wall and a second annular vertical wall;   a first horizontal annular wall connecting the first annular vertical wall to the second annular vertical wall; and   a plurality of openings through the first annular vertical wall.   
   
   
       13 ) The adjustable plastic manhole grade ring of  claim 12  further including a plurality of radially extending ribs extending inwardly from the second annular vertical wall and third annular vertical wall connected to the plurality of radial ribs. 
   
   
       14 ) The adjustable plastic manhole grade ring of  claim 13  further including a second horizontal annular wall connecting the second annular vertical wall to the third annular vertical wall. 
   
   
       15 ) The adjustable manhole grade ring of  claim 14  wherein the first horizontal annular wall is an upper wall and the second horizontal annular wall is a lower wall. 
   
   
       16 ) The adjustable plastic manhole grade ring of  claim 12  wherein each opening also extends through the first horizontal annular wall. 
   
   
       17 ) A plastic manhole grade ring comprising:
 a first annular vertical wall and a second annular vertical wall;   an upper horizontal annular wall extending radially outwardly from the second annular vertical wall;   a lower horizontal annular wall extending radially outwardly from the second annular vertical wall, spaced below the upper horizontal annular wall; and   a plurality of ribs extending between the second annular vertical wall, the upper horizontal annular wall and the lower horizontal annular wall.   
   
   
       18 ) The adjustable plastic manhole grade ring of  claim 17  further including a third horizontal annular wall connecting the first annular vertical wall to the second annular vertical wall. 
   
   
       19 ) The adjustable manhole grade ring of  claim 17  further including a seal on a first surface of the manhole grade ring for sealing to a similar manhole grade ring stacked therewith. 
   
   
       20 ) The adjustable manhole grade ring of  claim 19  further including a channel formed on a second surface for receiving the seal of the similar manhole grade ring stacked therewith. 
   
   
       21 ) A form set for a manhole grade ring comprising:
 a plurality of annular inner forms pivotably mounted to one another about an axis generally transverse to a center axis of each of the inner forms; and   an annular outer form, the inner forms also pivotable about the axis relative to the outer form.   
   
   
       22 ) The form set of  claim 21  further including a pair of laterally protruding sections extending outwardly from the outer form. 
   
   
       23 ) The form set of  claim 22  further including a hinge pin connected to the laterally protruding sections and about which the inner forms are pivotably mounted. 
   
   
       24 ) A form for a manhole grade ring comprising:
 a base; and   an adjustable portion have an adjustable height relative to the base, the adjustable portion having an upper annular wall and an inner annular wall.   
   
   
       25 ) The form of  claim 24  wherein the base includes a generally planar annular inner portion and an annular outer portion having alternating peaks and valleys. 
   
   
       26 ) The form of  claim 25  further including threaded members for adjusting a relative height between the adjustable portion and the base. 
   
   
       27 ) The form of  claim 24  further including a plurality of tapered radial ribs connecting the annular inner portion to the peaks of the annular outer portion. 
   
   
       28 ) A plastic manhole grade ring comprising:
 an enclosed body defining an annular cavity; and   an opening into the cavity for filling the manhole grade ring with supporting material.   
   
   
       29 ) The manhole grade ring of  claim 28  wherein the manhole grade ring is blow molded or rotationally molded.